Of course, as savvy as the IS hierarchy has been, I'd think they'd have a contingency plan but that has to be tempered against the man's ego. Time will tell.
For the sake of argument, let's say he is dead. What will happen to the Islamic State? Will there be a power struggle or mass defections to a less brutal way of life? It's hard to say.
We saw what happened when bin Laden was eliminated. Splinter groups went their way with much less cohesion. Not that they did any less damage; it just wasn't as well co-ordinated.
With Bagdadhi, however, it's not a bunch of rag tag cells but rather the beginnings of an actual state. I'd guess it's survival will depend upon the fervor and single mindedness of those left behind. It could go on as it has been or it could fall apart.
What would we have then? The remnants of the Sunni/Shia struggle for regional dominance with a lessening of the brutality. That's if you're willing to concede war is preferable to what IS has been waging - which is annihilating slaughter. Would each be willing to retreat to previously held territories as long as the opposition did the same and live in an uneasy truce? Talk about wishful thinking. If that would happen, however, it would be a good out for us.
With the brutal slaughter curtailed we could leave the Iraqi army to revamp themselves. The Free Syrian army could go back to trying to unseat al Assad and our advisers could exit the territory and leave the territorial strife where it belongs. Among the Islamic populations.
Again, time will tell. If he has gone to meet his bevy of virgins, however, I'd not get too cocky and figure air strikes can win any war. It could have just been a lucky shot.