It's just a matter of when the plug gets pulled.
With all the publicity that Letterman's retirement is getting, you would think that anyone was still watching the Late Show with David Letterman.
And you would be wrong.
By 2011, Nightline was beating both Letterman and Leno among young viewers.
“Nightline,” which had 1.248 million viewers in the 18-to-49 group (to 1.049 million for Mr. Letterman and 1.065 million for Mr. Leno)
Yes, that's how bad it was.
The media is crowing about how much Letterman's ratings have increased after the announcement that he would retire. (They were supposed to increase when Leno retired, instead he got beaten solidly by Jimmy Fallon.)
And the resulting surge of viewers was in and that meant that...
Letterman was solidly in second place in total viewers with 3.148M
Yes, that period is in the right place. Fallon meanwhile had 3.8 million viewers. Meanwhile Nightline beat Seth Meyers among young viewers.
It's obvious why CBS dragged in Colbert. They couldn't get Stewart and they have the top late night talk shows among the young viewer demo. This would be more impressive if they had any actual competition.
All it really means is that Colbert had about 1 million viewers in that demo. How many of them are going to follow him to CBS? Probably not as many as CBS thinks.
Colbert is a one-trick sneering pony catering to a limited audience. He can't do his old routine in prime time which dispenses the interest that audience has in feeling superior by watching him.
And it doesn't matter.
The late night talk show is done. It enjoys a niche following on cable, but in network form, it's over. It's just a matter of when the plug gets pulled.