He has a ton of PR to gain if he would come out and prove all of this to be just rumours. He could get a lot of sympathy and make more whites feel quilty that he was mistreated.Why cash this check right now. He needs to wait until the controversy breaks in the press. That's when he gets the maximum benefit from it.
“Hey America, you probably were not aware of it, but a few fringe, right wing nut cases have been alleging that I have been hiding facts regarding my birth certificate. Anyway, it was nothing but a smear campaign - you can all just forget that I mentioned it....” Sorry - but if true, he's now in way too deep. If false, no "Gotcha" bounce from the story.
He needs to control the timing of it so he can be properly prepared for it. He should present his birth certificate a day or two before the convention or maybe on the day it starts. That way he can use the convention as a platform to maximise its effect.
John