And what if he does? There are movie actors in Arab world, there is makeup, and it shouldn't be too difficult to imitate the voice of a man that hardly spoke to anyone in a decade. We were shown tapes of presumably real OBL that were in a much worse shape.
If he speaks it can be proven that it is or is not him. Appearances can be changed, but your voice is like a finger print or retinal scan. If Osama spoke on tape, it could be proven that it was him.
Naturally for people who want to believe conspiracies, no amount of proof would be adequate.
Frankly, I tend to agree with the administration on this one. It doesn’t make sense to release the Photos because there is no added value in doing so. The guy is dead and a gruesome picture will only be a propaganda tool for the terrorists.