I heard on NPR that legally Ohio has to continue counting all ballots regardless of concession speeches. Further, the concession speech is a formality and holds no legal weight. So technically, Kerry could concede, then still win Ohio and become President. Extremely doubtful, I know. But it's the only hope we have.
That was one of the most hilarious things about the last elections: Bush claiming "no callbacks, lock it, lock it no changes." Trying to put forth that Al Gore couldn't be President after he had called on election night to concede the race.
The man's a fucking four year old trapped in... The White House.