Bill O'Reilly's future at Fox News is the number one topic among Manhattan media executives, entertainment agents and journalists. But the network is keeping mum. Seemingly the only place where it isn't being discussed is on Fox News.

Neither O'Reilly nor Fox has said much about last weekend's report in the New York Times about settlements with five different women who accused the host of sexual harassment or verbal abuse. The matter has only been addressed briefly on Fox's air, and O'Reilly hasn't discussed it in the two editions of his show, "The O'Reilly Factor," that have aired since the story broke.

Fox's strategy of silence might make sense for now, given that O'Reilly is more than just a profit center for the company: he is an institution there, almost inseparable from the network, and long seemingly invincible.

Then again, that's exactly what media observers said last summer when Roger Ailes was sued by former Fox News anchor Gretchen Carlson for sexual harassment. Ailes resigned two weeks later.

As Ailes faced an onslaught of sexual harassment allegations, several of the network's on-air personalities strenuously defended him in the press. And when O'Reilly faced a sexual harassment lawsuit in 2004, he delivered a ferocious response on-air the night it was filed.

Now, though, even as more than 40 advertisers have dropped his show, O'Reilly and his network aren't fighting back publicly.

Related: Trump defends O'Reilly: 'I don't think Bill did anything wrong'

Fox News' relatively subdued response has driven speculation throughout New York media about whether the longtime king of cable news could be on the way out -- and whether such a scenario is even plausible. Most would have dismissed the idea offhand at any other time, but the marked contrast between Fox's strategy in the past compared to now is fueling the discussion.

It could be a sign that network mogul Ruper Murdoch and his sons are following through on their pledge to remedy the network's culture.

On the other hand, the Murdochs might be quietly circling the wagons, demonstrating the same type of loyalty that Ailes inspired in many of his employees and perhaps bowing to financial reality.

Fox renewed O'Reilly's contract knowing that the Times story would be coming out. The Washington Post reported that the new deal extends at least through 2020.

Contracts have clauses and escape hatches. But if it really goes to 2020, those could be very expensive for the network.

Then there's the matter of a replacement. Fox has no obvious person in line to succeed O'Reilly right now.

"They are running plays from the Roger Ailes playbook and it is out of date," said one media executive at another company. "The Murdoch sons were supposedly 'disgusted' by Ailes' style and tactics, and couldn't wait to run him out of the company -- but if imitation is the sincerest form of flattery, they seem to be heaping praise on Ailes this week."

Related: Why Bill O'Reilly and Fox News might be able to weather advertiser storm

Of course, there could be millions of reasons why Fox News is standing by O'Reilly. As in millions of viewers, and hundreds of millions of dollars.

"The O'Reilly Factor" has been the no. 1 program on cable news for 16 years running, and it's coming off the best quarter of ratings it's ever had.

On Monday, the show demonstrated its ratings prowess once again, drawing 3.65 million viewers -- far more than any of its competitors. It's also a cash cow. "The O'Reilly Factor" generated more than $178 million in advertising revenue in 2015 and over $118 million in the first nine months of 2016, according to Kantar Media.

An on-air personality at a rival network said O'Reilly is a "holy grail" for advertisers.

"You can't go alt-right if you're a major corporation," the source said. "He's as far as you can go to reach older, conservative Americans."

The exact fallout of the advertising exodus isn't clear yet. Paul Rittenberg, Fox News' executive vice president of advertising sales, said in a statement Tuesday that the network was working with advertisers to "address their current concerns about the O'Reilly Factor," and that "the ad buys of those clients have been re-expressed into other FNC programs."

That would suggest that the advertising revolt, such as it is, hasn't affected Fox's bottom line -- at least not yet. Mercedes-Benz and Sanofi, two companies to withdraw from the "Factor," both confirmed to CNNMoney that their ads would be re-allocated to other Fox programs. Only one organization, the Society for Human Resource Management, said it had ended its advertising on the entire network.

Related: Read what Bill O'Reilly's sponsors are saying about 'disturbing allegations' of harassment

Richard Levick, a public relations specialist who has worked in crisis management, said that "it's going to have to get very costly" before Fox shoves O'Reilly out.

"This is all about the math," said Levick. "This is not about doing the right thing. If Fox was interested in doing the right thing, it would have done it long ago."

"The question that Fox has to ask is, are viewers going to start getting asked by their children: 'Why are you watching this man?'" he added. "And once Fox feels that that moment's come, that will have as much, if not more, resonance than the advertising dollars."

Levick said that we're living in the "age of mercantile activism," which could change the equation for the advertisers -- and for Fox.

"If the ads are just being reassigned to other Fox shows, it temporarily gives companies the opportunity to do the right thing and look good," said Levick. "But as mercantile activism continues to evolve, consumers are going to begin asking why they're spending money on the network at all."

The racial justice organization Color of Change intends to ask that question forcefully. The group called on advertisers to drop O'Reilly this week, and Rashad Robinson, its executive director, said he will be "monitoring what these companies are doing."

In 2009, the group spearheaded a similar campaign aimed at advertisers on Glenn Beck's Fox News program.

O'Reilly has weathered controversies before, often emerging from them with even more power, but Robinson thinks this time around could be different.

"At the end of the day," Robinson said, "money speaks to the Murdochs."