Otherwise, we'd have seen more attacks
I pray you are correct. But Al Queda generally takes a fair amount of time between attacks.
If bin Laden is alive I would not count him out just yet. As dirtboy says al Queda takes some time between attacks. It takes time to set up a coordinated attack like 911.
You also have to consider we complete destroyed the al Queda home base. It will take a considerable amount of time for Al Queda to reorganize and train a new batch of jehadist.
Al Queda cant be considered out for the count yet. 911 gave them a lot of publicity in the fundamentalist Muslim world. I believe they will have eager young men and women with dreams of a glorious martyr's death flocking to bin Ladens banner.