Al Zawahiri takes control of AQ, or gets one of the OBL doubles to appear on Al Jazzera. If you chop off the head, another will rise in its place, the only question being - who has the charisma and the $$$$ to fill OBL's big shoes. If the US could prove beyond the shadow of a doubt that OBL was dead, then the claims of martyrdom would have significant effect. No doubt, AQ would suffer significantly, losing access to OBLs vast financial base. But killing OBL would cost the US too - there's just too much to gain in keeping him alive to seriously consider knocking him off. Is it possible that POTUS knew that he wouldn't be there at zero hour? Seriously, the amount of opportunities to knock him off have been staggering, and yet, he always manages to escape, most of the time on a donkey.