Craig Ferguson has stated many times that he wouldn't want the earlier slot. He, for the most part, get's to do his show how he wants to do it.
For example, the anniversary show that he did with all puppets, except for the guests. He has a lot of repeat guests he is just visibly having FUN with bantering on his set. He tries to have his quests have fun on his show, rather than worry about pushing their latest product. *Case in point, his recent guest Gina Carano, he really saw she wasn't comfortable yet with being on talkshows, and got her to relax and have some fun*
He can change the format of the show now and then, to do something HE wants to do, i.e. The Stephen Fry interviews, Bishop Desmond Tutu, when James Earl Jones was on the show, etc.
If he could keep the same level on control over what he was doing, he'd probably consider it, but he knows that's not gonna happen.[DOUBLEPOST=1397196392,1397195982][/DOUBLEPOST]As far as Stephen Colbert goes, he has a Warchest of Comedy/Entertaining/Interview skills that go far beyond what the narrow focus of being "Stephen Colbert" has shown most folks.
He won't be "Stephen Colbert" (well, I'm hoping he'll pop up now and then) . He'll be Stephen Colbert, and I look forward to his show.