Well the 2001 idea wouldn’t seem to fly because he has done video referring to later events. I remember that he was supposed to have some medical conditions and he looked prett bad early on.
If he has died, I can’t see why it would be in the Bush administration’s best interest to keep him alive, they weren’t even pretending to try to find him anyway. It would seem better to kill off the titular head of the beast.
As far as where he is today, maybe it’s like the movie Sleeper where the Great Leader continued to communicate with his people while in reality they were desperately trying to clone him from his nose, all that was left after an assassination attempt.