There is where you are wrong. His followers do not believe with 100% certainty that he is alive. No way. There can be no doubt Bin Laden (if alive) has had to be terribly disappointed with how the Taliban and Al Qeada and Muslims within the Countries he thought supported him have fought. They have lost eaisly in every battle. Bin Laden did not expect this (at all). He believed the "press clipings" of how USA going into Afghanistan would be another defeat like it was for the Sovit Union. He truly believed this.
However, the exact opposite happened. And his followers regardless if he is alive or dead have not fought for him like he is alive commanding officer directing them into battle. So the notion that his followers aready believe he is alive is 100% false. You can see this by their lack of counter attacks just within Afghanistan itself. Not to mention other countries within the middle east.
And give me a break. Saddam didn't change his appearance by growing a beard. That does not really change one's appearance. I mean come on. Saddam wasn't showing himself in public and getting by with it...because no one recognized him with that "beard"...But more to the point, Saddam did release a video "proving" himself alive. He did exactly this!! You cannot deny that. He did put out a video with up to date information regarding the war "proving" himself alive.
Bin Laden also did this up until Dec 2001.