I don't think if Ukraine would be able to retake Crimea in any scenario. The population there (except for the small remaining population of Crimean Tatars) is very pro-Russian, much more so than even in the Donbass. Thus Ukraine loses one of its best and strongest advantages in this war: fighting on friendly (at least more or less friendly in the Donbass) home turf in Crimea.
I see Crimea as much more realistic than reconquering the Donbass, simply because the latter borders Russia itself.
If Ukraine is able to cut the land bridge (big if..) they should by now have enough long range missiles to be able to stop most of the Russian supplies coming into Crimea by sea, air and across the bridge, if so the Russians (incl. the settlers) would eventually either have to leave or surrender. I don't see why Ukraine would have to actually invade Crimea to take it back, at least not before such an invasion would mostly be a mopping-up operation.
