Laden could be dead.
Zawahiri is not.
Wait! I got a new theory. Remember how those Zawahiri audi tapes sound distant and scratchy - this in an age any poor Pakistani could afford a cassette recorder making a cleaner recording?
Maybe the tapes are purposely made that way to make the effect Zawahiri is in some hut in Pakistan - rather than comfy abode in Iran.
I would bet that Zawahiri is living a very comfortable life in some private Mullah controlled estate in Iran. He is being kept there, finance and equiped with the communication gear to control/direct the terrorist activities in Iraq by the mass murdering Mullahs of Iran.
Hopefully the Israelis, the Brits or us will get a fix on him and the same thing that happened to the train in N Korea can happen to him.