I don't think Warner has a lock, but I do think he has better odds than HRC, Clark, Edwards, Gore, Kerry, Bayh, Feingold, or anybody else whose name I've heard bandied about. To improve those odds, I'd add Senator Bill Nelson of Florida to the ticket -- a 3-4% "vice-presidential favorite son" boost should be sufficient to put the Sunshine State in our column, and I think the rethugs would have a very hard time finding the electoral votes among the states Kerry won to compensate for losing both VA and FL. Not impossible, especially if they go stark raving sane and nominate someone like McCain or Giuliani, but unlikely.
I would also Suggest either a Clark/Easley or Easley/Clark Ticket