In order to retain any cohesiveness in the organization, the new leader, or those vying for the position, will have to loudly take credit for some new attacks. The greater the horror, the better. I think the first affirmation of Z's death will come in this manner. The military won't announce anything until they are 100%. How long does a DNA test take, anyway?
The biggest thing going against this story is that the attack took place in Mosul. And, we have been taking down the leadership of al-Qaeda in Mosul on a daily basis. The al-Qaeda network in Moseul has had its teeth kicked in. I have to think that Z-man would avoid Mosul like the plegue.