And as the heading of this post says, only if Barak Hussein Obama and his advisors have massive collective brain malf.
As far as I know, replacing one's running mate mid-campaign for reasons other than illness is unprecedented in American politics. If BHO replaces Biden it will ring the death knell for his campaign, because a) he'll obviously be reacting to McCain's campaign (particularly if he replaces Biden with Hillary); b) it shows he doesn't have any confidence in his ability to make a decision and stick with it; c) it would show beyond a doubt that BHO was in this only for the power and not for any particular principle.
In the first case--replacing Biden with Hillary--although the Democrat loyalists would immediately return to the fold, too many of the mythical "moderates" could be turned off by the move. The move would clearly be a reaction to McCain's selection of Sarah Palin, and BHO would obviously be engaging in "me-too-ism".
Second, if Biden was such a great choice, why the hell would BHO replace him? Why didn't BHO pick Hillary in the first place, if Hillary is preferable to Biden? This would show that BHO may not have all the decision-making capacity that a President needs; thoughtful moderates may abandon him rather than vote for an indecisive person who tossed his running mate under the bus because he wasn't a girl.
Third, the fact that BHO throws people under the bus if they impede his forward progress is a major turn-off for everyone but the hardcore Democrat loyalists.
And a fourth point: would Hillary even agree? If it was me, I'd say "Thanks, but no thanks" to that BS--but then again I'm not a power-hungry harridan. Having looked over my prior posts on this election I've proven to be a poor predictor of what Hillary will do to obtain power; but I have to believe that even her desire for power has its limits. Would she accept the VP nod after BHO tossed Biden under the bus? Or would she worry that BHO might toss her under the bus if she became inconvenient?
My own instincts tell me that the BHO campaign is not planning to dump Biden, that it would be a stupid, stupid move on their part. Americans want a President who is confident and self-assured, though not to the point of arrogance; someone who waffles on his VP pick two months before the election is not going to come across as a good choice. Dumping Biden would cost them critical votes, and if there isn't someone on the campaign staff that knows that, the Democrats may be in for a world of hurt in November.