It doesn’t matter if ISIS’s leader or Al Qaeda’s leader was killed, because islam was left, and that’s what made them, and what will make their replacements, and what will make the replacement’s replacements and so on...
I think Al Qaeda’s leaders realize that ISIL atrocities are too extreme even for very conservative Muslims. Al Qaeda knows that ISIL is so bad Islam is loosing support even within Islamists who want Sharia Law.