Punk is not going on the fucking Ultimate Fighter. He's too prideful for that
(I will preface this by saying that I am a big punk nuthugger by this forum's standards)
Actually, there are several reports saying that Punk wanted to go to lower companies before receiving the offer from the UFC, and he went as far as saying that he was willing to go to TUF, but Dana said he could go to a main card and it was essentially a no-brainer.
You might think it's bullshit, but literally every piece of information I ever came accross on this stated that Punk was obsessed with doing MMA far before Dana contacted him. I really don't see why he wouldn't want to go to TUF, assuming he is in it for the fun and knowing he never said he thought he could be a world beater, it's disingenuous to assume literally everything he has no basis on truth whatsoever, specially when compared to the other things celebrities can do after retired, he had almost nothing to gain from this whole ordeal.
As a Sidenote, I want the UFC create a celebrity TUF, so I can watch rich people beat the shit out of each other.