A recent NYTimes story suggests that Bloomberg would enter an Obama- Huckabee match up.
I doubt it.
Suppose Obama wins the democratic ticket. Since Obama's support comes partly from independents and moderate republicans (more here), Bloomberg would be facing a very tough contest against someone who would have the organization and momentum from the primaries (although beating the Clintons could take a crippling toll on Obama). Idealogically, Obama and Blomberg are pretty close (which has been driving many on the far left crazy).
If Bloomberg is really running to win (rather than to entertain his ego), an Obama democratic ticket would prevent him from running since Obama's message would leave little room for Bloomberg's pitch for a bi-partisan pragmatic approach to pressing problems.