Well the thing is, we put a huge dent in Al-Qaeda, a HUGE one at that.
I mean, we're talking about one of the biggest terrorists, who also formed the largest terrorist organization (Al-Qaeda, at least to my knowledge). So taking him out was a big impact no doubt.
I do believe that Al-Qaeda will take one of three paths:
--Dissolve, and eventually disappear.
--Reappoint a Leader, or Council maybe, and continue to be terrorists.
--Reappoint a Leader, or Council maybe, and plan a large-scale attack on the USA.