TOKYO -- Beijing's political nerve center has been abuzz since last week with rumors of a bombshell whose implications could reach deep into the 2030s.

For the first time in months, perhaps years, the fate of China's future leaders has become the hot political topic. "The idea of appointing Chen Min'er as China's president and Hu Chunhua as the country's premier was supposed to have fizzled out," said a source who keeps up with the hubbub in the Zhongnanhai area, which houses the offices of China's leaders. "But it remains intact."

Another Zhongnanhai source was equally shocked. "This is the biggest riddle President Xi Jinping has thrown at us to date. It will take three years to solve."

Speculation over future Chinese leaders was reignited in the middle of this month by Xi's high-profile inspection tour of Chongqing, one of four municipalities directly controlled by the central government. Beijing, Shanghai and Tianjin are the other three. Chen Min'er is the city's top official.

Chen is a leading figure in the "Zhejiang faction," a tight-knit group of officials who worked with Xi in the eastern province, home to the World Heritage West Lake, in the early years of this century. Chen was once tipped as the most likely candidate to succeed Xi as China's top leader.

In this respect, Xi's inspection tour of Chongqing was not surprising. It looked like a reward for a close and loyal aide.

The bombshell was the presence of Vice Premier Hu Chunhua, 56, at Xi's side during the inspection tour. While Hu is technically in charge of poverty eradication, the main objective of the tour, the Chongqing location and the images of Xi flanked by Chen and Hu sent shock waves.

Xi's bag carriers were the usual bunch. Vice Premier Liu He, 67, ditched his duties as chief negotiator in the U.S.-China trade talks to be with the boss, alongside Ding Xuexiang, 56, the director of the Chinese Communist Party's General Office, or more specifically Xi's personal secretary.

Surrounded by die-hard loyalists, Hu looked like a guest invited into the Xi faction's team-bonding retreat.

Hu is the best and brightest of the Communist Youth League, a massive organization that Xi has seen as the stronghold of his adversaries. It currently boasts nearly 90 million members.

The league is the power base of former President Hu Jintao, 76, as well as his de facto disciple and current Premier Li Keqiang, 63.

Contrary to tradition, an official who took the helm of the league as its first secretary recently missed out on a big promotion. This was likely due to Xi, a shrewd politician who pulls no punches.

Hu Chunhua has similarly suffered. While assuming the prestigious post of vice premier, Hu has not been assigned many high-profile tasks.

Officially, Hu oversees part of China's economic policy. But he has taken a back seat to fellow Vice Premier Liu He, the trade negotiator. After years of being in the spotlight, the onetime influential figure can no longer attract the gaze of China's state-run media.

Why then would Xi put Chen and Hu on the same stage?

Back in March 2018, Xi revised the Chinese constitution, which had limited a president to serving two five-year terms. By striking the limit, Xi allowed himself, in effect, to stay in office for the rest of his life.

But Xi's highhandedness generated a strong backlash within the party, especially among elders who remember the 1966-1976 Cultural Revolution, which led to Mao Zedong's calamitous dictatorship.

Xi has significantly consolidated power with a blistering anti-corruption campaign. But criticism of his "dictatorial ways" within the party has a politically debilitating impact; it hits him like a body blow.

Xi is now taking another blow, from the U.S., which is damaging his economic management reputation. The situation is serious enough that it could eventually cause Xi to lose his political stamina and erode his unrivaled power.

Hemmed in, Xi served up the succession riddle. But it is likely more of a political tool than riddle, one Xi is wielding as the party begins to anticipate its next national congress, in 2022.

(Click here for a guide to China’s leadership hierarchy)

A turning point of Xi Jinping's strategy to become a "retired emperor" with real power came at the party's 19th National Congress in Beijing in 2017. © Reuters

The vast majority of party members have no doubt Xi will remain China's de facto leader, up to and beyond 2022. But how will he foster the leaders who will follow him? There are at least three possible scenarios.

In one, Xi, 65, keeps the current system and stays on as China's president, or head of state, and as the party's general secretary, or No. 1 in the party hierarchy.

In another, Xi restores the post of party chairman, which was held by Mao, and assumes the post while ceding the presidency and general secretary title to younger leaders.

In a third scenario, Xi retires as both Chinese president and as party general secretary and hands over real power to younger leaders.

Few people, if any, believe the third scenario to play out, and there are strong party objections to the first scenario. So is it time to prepare for Chairman Xi?

If Xi is to become a "retired emperor" with real power and continue to rule China, he will have to choose a new premier as well as a new president-cum-general secretary.

A turning point came in the fall of 2017, when the party held its last national congress. During the event, a proposal was rumored to have been made, calling for the future appointments of Chen Min'er as China's president and party general secretary as well as Hu Chunhua as China's premier. The proposal apparently also called for Chen and Hu to be promoted to the seven-member Politburo Standing Committee, the party's top decision-making body, led by Xi.

The combination of Chen and Hu resembles the combination of China's current top two leaders, President Xi and Premier Li.

After laying low for a couple years, Vice Premier Hu Chunhua, left, and Chen Miner, secretary of the Chongqing Municipal Party Committee and a member of the 18th Central Committee, are back in the spotlight. (Photo by Kosaku Mimura)

Li had long been seen as the most likely candidate to succeed Hu Jintao as China's president and party general secretary. But Xi, an elder dark-horse candidate, came from behind to win the race.

Hu Chunhua is currently serving a second term as a Politburo member. The Politburo has 25 members, including the seven Politburo Standing Committee members. Meanwhile, Chen is serving out a first term as a Politburo member. Chen, 58, is two years older than Hu.

But Chen and Hu were not appointed to the standing committee. Hu assumed the post of vice premier while remaining a Politburo member. Chen moved from Guizhou Province to Chongqing to become the municipality's top official. He was promoted to the Politburo.

Chen, who at one point was frequently in the news, has attracted considerably less attention during the past two years. In fact, fewer domestic and foreign journalists last month covered the Chongqing subcommittee meeting during the annual session of the National People's Congress, China's parliament, than did a year earlier.

As for Chongqing, the crucial city's economy has been performing poorly.

Hu has also been attracting less attention.

The prevailing view has been that Xi will retain his positions but Chen, Hu and other "sixth generation" leaders -- those mostly born in the 1960s -- will miss out on top posts.

At the next party congress, Chinese President Xi Jinping will be 68 and reach the traditional retirement age, but Premier Li Keqiang, two years younger than Xi, will not. © Reuters

In a new twist, however, Xi's tour of Chongqing has cast the spotlight on the Chen-Hu duo once more. Many Zhongnanhai sources now wonder if the proposal to appoint Chen as president and party general secretary and Hu as premier has survived.

The party mood soured after Xi pushed through his president-for-life constitutional revision. Xi responded by treading lightly, an apparent attempt to quiet criticism of him as a dictator who does not bother to foster future leaders.

If Xi remains China's de facto top leader and taps Hu as premier, that in itself could be a curveball. It would mean the end for the current Premier Li Keqiang.

To Xi's disadvantage, Li is two years younger and unlike Xi, will not have reached the customary retirement age of 68 at the party congress in 2022. It may be difficult for Xi to force Li to retire due to age. It also seems that Xi is encouraging Hu to pledge loyalty to him by dangling a carrot.

"We will see a partial outcome of the battle next year," a Chinese political source said. This will foreshadow the personnel changes to the Politburo Standing Committee due in 2022, at the party congress.

Xi seems to know that with his political momentum showing signs of a slight decline, next year will be crucial for him.

Katsuji Nakazawa is a Tokyo-based senior staff writer and editorial writer at Nikkei. He has spent seven years in China as a correspondent and later as China bureau chief. He is the 2014 recipient of the Vaughn-Ueda International Journalist prize for international reporting.