In short it won't last 5 minutes.
The Israeli's don't really want to negotiate with "terrorists" who basically can't be trusted, Hamas though having the cr*p kicked out of them are still working on the principal that they're winning when all they've got, as regards the upper hand, is the hostages and they know that once they return ALL the hostages Israel is really going to go after them, and knowing Israel the last 15 months will seem like a picnic in comparison.
Although Israel is guilty of overkill {excuse the pun} it would be bad for Israel, and the middle east, to let Hamas "regroup" which is what they will ultimately do.