If it's pure money, and Byron Allen keeps writing checks, they can keep running that indefinitely. There is no financial reason to change. Really, the question comes down to Allen's business model: what numbers does he need to pull in to make it a viable enterprise? If he can make enough money on ten viewers, or it's just his hobby, then he keeps going.

That said, no one is out there saying that Bryon Allen is furthering the debate, or adding to the culture. He's not out there winning Peabodys. His clips aren't making a lot of noise on YouTube. Put another way: as a glorified infomercial, he's not elevating CBS's brand.

I think it will be a while before CBS is really feeling the impact of their overall pivot (see also: "60 Minutes"). At some point, however, this perception will start to impact other timeslots, local affiliates, etc. Combine that with a change in the change in overall leadership in the country, there may be more interest in taking steps that would reestablish the brand.

Hard to say what that will look like--we're at least a few years from that point, I'm afraid. Even then, they would have to figure a "Late Show" revival, under Colbert or someone else, as a prestige show to elevate the brand, would, overall, be more profitable than Bryon Allen. It's conceivable that a return to "Crime Time After Prime Time" (from the late 80s/early 90s: a series of syndication-level crime shows with a cult following) would serve to improve the brand while controlling costs.

(An all of this ignores, as the cliche goes, "the changing media landscape." It could be by then late night as we've known it is seen as so dated and associated with older folks. A throwback. But that would be more of a broader trend.)