What incentive do they have at this point to return to the old status quo?

If the US fucks off, then Iran is left in a powerful negotiation position. They could us this incident to help normalize relatuons with oyher gulf states by pointing how the US and Israel started the fight, then left them all high and dry. They could make non-agression and safe passage deals with the gulf states as well as exhert real pressure against the normalization of relations with Israel.