Hasn't Osama released an audio tape since our invasion of Iraq, where he specifically mentioned "Iraq"? I thought I remembered he had and that it had been authenticated.
If he is dead he's died since then.
We have to assume he is still alive. We have to continue to look for him until we know for sure.
The initial take on the tape was that it was of too poor a quality to authenticate. After that the government left it up to the press to make of it what they would. And they did. Bin laden alive sells more product for a far longer time than OBL dead. It is good for the Nertwork News.