It won't be Cuomo, Brian Schweizer or Mark Warner.
Whys that?
He thinks their too conservative. Cuomo is a Clinton-like "New Democrat". He is a fiscal hawk but a social liberal. Brian Schweitzer is a moderate populist Governor of a red state. Mark Warner of a Fiscal conservative and a social moderate.
If Romney wins this year, the Democrats will turn right. Unless it becomes clear that Obama lost because of Jill Stein or Rocky Anderson taking away too many left-wing voters. And the odds of either of those two getting enough media attention to have a spoiler effect are dismal.