Bush would do what Kerry is doing...
...which is to place his concession in abeyance until he's absolutely certain he's lost. Certainly can't fault Kerry too heavily for that, and I wouldn't I would fault Bush if he were in the same position.
However, the "provisional" ballots may or may not make a difference. There may not be enough valid provisional ballots to change the outcome as it stands right now. That is to say, the state of Ohio will have to toss any ballots submitted by unregistered voters, underage voters, known felons, fictional characters and dead folks.
Once the provisional ballot "chaff" is tossed, there will likely be little Ohio "wheat" upon which Kerry may rely, as it may become obvious that there are not enough provisional ballots to change the outcome. The actual counting of these provisional ballots may be any number of days away, however.
So it isn't surprising that Kerry would delay conceding until the provisional ballot count becomes apparent. I doubt the Bush camp would do any differently, since both campaigns have spent vast sums to get to this point. Neither would elect to concede prematurely.