I can't see how Osama being captured or killed would in any way be likely to reduce the ability and determination of people in the Al Qaeda franchise to carry out their murderous activities.

When one leader goes, there's always another. I am reminded of the way that Hitler is supposed to have been enormously encouraged when he heard that Roosevelt had died, and appears to have thought it would somehow make a huge difference. Of course it didn't, because that's not how things work. (And no, that doesn't mean I am suggesting Bin Laden is like Roosevelt - this is a strictly limited parallel. However some people do seem to have difficulty in understanding that concept, so I thought I'd underline that.)