Along with many other traditional pursuits, the world of rugby is hurtling towards a future it can barely comprehend.

At the Hong Kong Sevens, Kenya are genuine threats and Brazil are appearing for the first time. A 40,000 crowd watched Madagascar beat Namibia last year, with 15-a-side interest also rising in Thailand, the Philippines, Moldova and Venezuela. Afghanistan now has a national team and Guangzhou in China is due to host a leg of the women's world sevens next week.

And on it goes. Welcome to a sport exploding in myriad different directions. In Russia there is such a well-established, professional league that players relocating to the English Premiership have to take a pay cut. In the United States the sport has obtained "varsity" status which means college rugby scholarships are now on offer. Several South Africans have already packed their bags; you suspect one or two British teenagers may also fancy the frat pack experience. A souped-up American national side really would make multi-national sponsors sit up.

If they prefer, they could head for Medellín, Colombia. "We've had incredible stories coming out of Colombia," says Mark Egan, the International Rugby Board's head of development and performance. "They've got 10,000 registered players and the government are now investing heavily in rugby. They see it as a fantastic sport for young children and they've brought it into young offenders' institutions. In Medellín they've built a rugby centre with two artificial pitches, changing rooms, the lot."

All a long way from home? Not really. One rung below the Six Nations, a hugely competitive European Nations Cup has just finished. While Wales were stampeding to their title, Georgia confirmed their rising status by securing the second-tier crown. Their New Zealand coach, Milton Haig, believes good progress is being made: "I'm confident that in the next six to 12 months we could, if we get an opportunity, put the frighteners up a tier-one nation."

The word "if" is the crucial one. Exciting new markets or not, the Six Nations still clings to its old upstairs-downstairs structure, which means Georgia can only hope to play the grandees above them every four years at a World Cup. Imagine if this year's wooden spooners, France, had to go to Tbilisi for a mandatory play-off next month to retain their championship status? The commercial implications of defeat might scare the daylights out of the major unions but imagine the frenzy of interest elsewhere.

"We know Georgia is a union which can perform if it gets the right investment," says Egan, who visited Tbilisi last autumn with the ex-All Black captain Graham Mourie to meet the new Georgian prime minister, who has overseen a £20m investment in 11 new high-performance centres around his rugby-mad country. In 20 years' time we may all be wondering how the closed-shop arrangements endured for so long.

This, however, is not a vision shared by the Six Nations' chief executive, John Feehan. As he tots up the championship's soaring global viewing figures, he finds it hard to believe anyone would wish to tinker with such a winning formula. "To be brutally honest, I couldn't see a change in the next 10 years," predicts Feehan. "You've got to look at what you've got and at the moment we've got an extraordinarily successful tournament.

"You change it at your peril. We'll never say never but at the moment I think there is a big gap between the bottom Six Nations side and the next-best team."

The evidence, however, is less conclusive than it was. Georgia lost only 15-6 to Scotland at the 2011 World Cup and, by common consent, they and their rivals are improving. Last week Georgia and Romania shared a 9-9 draw in Bucharest and the Lelos only sneaked home 17-13 against a competitive Belgium side in Brussels. The latter were a lowly 58th in the world a decade ago, while Romania are now coached by Welshman Lyn Howells.

Of the £10m per year invested by the IRB through their strategic investment programme, some £500,000 apiece goes to boosting standards in Romania, Georgia and Russia, but Feehan makes clear the Six Nations is not a charity. "I don't think putting Romania or Georgia into the Six Nations would necessarily be good for them, or the competition. Quite frankly, the IRB has never contributed to the Six Nations' success. It's owned and run by the six unions."

More encouraging, at least, is the fixture schedule for the 2015 World Cup which, thank goodness, will be fairer than any of its predecessors. The leading nations – and broadcasters – have finally agreed to midweek dates for the top sides, ensuring the minnows will have similar rest periods to everyone else.

For countries like Russia, it is something to cling to. "We are ambitious to be a major rugby nation but there is no pathway for us to go up," says Russia's chief executive, Howard Thomas. "I'm a huge Six Nations fan, but the world has got to ask: 'Is it good for the global game for it to stay as it is?' We need to have that debate. At some stage an established side will be beaten and people will say: 'This tournament doesn't represent the best six teams in Europe any more.'"

In the meantime, more cross-border club fixtures is one obvious compromise, although that raises its own issues. It takes eight hours to fly from London to Siberia via Moscow if, say, Saracens were drawn against Russia's current champions, based in Krasnoyarsk. Then again, the world grows ever smaller. Last month Leicester organised a training camp for youngsters, not in Market Harborough but Kuala Lumpur. Asia, with a World Cup in Japan in 2019, looks ready for major growth.

"Super Rugby may look to expand its horizons in 2015 and the Asian market is on its doorstep," predicts Egan. "There's already a professional league in Japan and there are opportunities in Hong Kong or Singapore to put franchises in. There are plenty of options to transform domestic competition models. Over the next five years that's where the game is going to have to look at itself."

Within that timescale, too, rugby sevens will have featured at the 2016 Olympics. Marcos Paixao's modest home in Rio's Contagalo favela is a long way from the game's cosy heartlands but, as the IRB's Total Rugby programme highlighted this month, that is no longer a barrier to oval-ball passion. Marcos and his three brothers were introduced to the sport as part of a special project to help the city's poorest kids and now belong among the 15,000 active rugby players in their football-obsessed country.

Of course there are still pitfalls. The rise of sevens can have a knock-on effect, particularly in China where funding for fifteens has suffered. There is a global audience out there, however, craving a piece of the action. "There's still a huge challenge to bridge the gap but we're doing as much as we can," says Egan. "There are also 205 national Olympic committees now interested in rugby as well." The future may arrive sooner than we think.