In anticipating any such regional changes, it is important to distinguish actual interests and likely post-agreement behavior from what regimes may say disingenuously for effect today.
This is most obviously the case with Israel, where smart people concerned about a possible Iranian nuclear weapon realize that the object of their concern is much less likely to materialize with an agreement than without one, but where the right-wing government is doing everything it can to kill a deal in order to keep Iran in the international doghouse, suppress it as a competitor for regional influence and U.S. attention, and retain it as an all-purpose bogeyman to distract attention from things the Israeli government would rather not talk about.