One dinnertime chat does not a ticket make, though it would certainly confirm my impression that Chuck Hagel is less a principled anti-war conservative than an unprincipled attention-whore. (And I say this as someone who would like to see a principled anti-war conservative in the '08 race - and one who's a little more plausible than Ron Paul.) What's more interesting, to my mind, is the question of whether there's any combination of Republican and Democratic nominees that would provide a natural opening for Bloomberg to run as an independent. It's hard to imagine, for instance, that he would get much oxygen in a Giuliani-Obama contest - there would already be one pro-choice New York Mayor in the race, the Dems would be so excited by their candidate that there wouldn't be much room to peel off left-leaning independents, and the only disgrunted voters looking for a candidate would be social conservatives, hardly Bloomberg's natural constituency. What he would need is a race in which the other two candidates are perceived as extremists, particularly by the national media - which would be Bloomberg's natural constituency. So if, say, George W. Bush ran again, opposed by Howard Dean, the opening for Bloomberg would be obvious - but that doesn't seem terribly likely, does it? Nor does a Duncan Hunter-Dennis Kucinich battle royale, and so forth.
Failing that, Bloomberg might be able to capitalize on a situation in which the two nominees are perceived as respectable but highly-conventional representatives of their respective parties - but I don't think you're likely to get that this time around either, at least not in the way that gives Bloomberg an opening. What he needs is a Republican who's a conventional right-winger on social issues and a Democrat who's a conventional lefty on economics, and few of the plausible general-election matchups fit that bill. I suppose Romney versus Edwards comes closest (that is, post-2004 Romney versus Edwards), but if that's the general-election pairing I'll buy a hat and eat it.
The more-plausible year for a Bloomberg run, in a way, was 2004, when both candidates were flawed and polarizing figures and there was clearly room to run between them. Though on the other hand, the stakes in that election were taken (erroneously, I think) to be so high that very few voters would have been willing to risk throwing their vote away - something Americans seem to have an inordinate fear of doing - by casting it for someone not named Bush or Kerry.
That said, Bloomberg does have enough ready cash to pay thirty million people two hundred bucks each to vote for him. So he's got that going for him.