If the ref stops the match because Punk can't continue, he wins the title. That's a KO win, they've happened pretty frequently. Tensai even beat a few people like that when he came in.
Don't WWE always say in Championship matches, the Title can only change hands via pinfall or submission? Obviously a KO win in a normal match is a regular win, just like a DQ win or a countout win is, but if you win by KO in a Title match, do you get the Title? I don't recall it ever happening.
I can actually see them doing that to be honest. Punk needs to retain anyway, giving the belt to Skippy boy would be disastrous. I don't even really dislike Ryback, but giving it to anybody would be disastrous, Punk's reign needs to remain uninterrupted until the Rumble.