My money's on Gingrich/Jindal to win the GOP civil war.
Evangelicals like him. Low tax business folks like him, he's viewed as an "ideas man," and, to many GOPers, he harkens back to their "storming the gate" moment in 1994.
I don't know if he ever formally takes over, and I don't know who his RNC chair choice would be, but I would bet Gingrich ends up with the most influence.
Probably the surest tell is to watch the fortunes of La. Governor Bobby Jindal, his favorite current acolyte, who he desperately tried to push on the McCain campaign as a VP selection.
(I would say Romney as the other likely, but I'm not exactly sure who his power base/backers are. (And it looks like Palin is done.))