I doubt it will be McCain, If George W. Bush lost the election and everyone regretted not having george then it could be jeb, but if bush wins I think rudy if he gets elected or appointed something because he's endorsed others like thune, my personal choice would be bill frist for president and rudy or mitt romney for vice president, it would get the south and some of new england.
Personally, I would like to see Jeb. But the "dynasty" issue will rub huge swaths of the public the wrong way.