While these scenarios are possible there are many other likely outcomes. If the Russia military continues to perform poorly and Ukraine continues to get support of Western countries. (Both of which are likely) Ukraine may have the ability and motivation to go on the offensive and push Russia out of the Donbas and potentially even Crimea. It’s important to remember that while Russia controls Crimea it is an occupation. Not even China recognizes Russia’s claim to any part of Ukrainian territory. The Ukrainians certainly do not and they want the Russians out of their country. If Ukraine can continue to gain traction and keep the advantage they will have less reason to negotiate for anything less than the full withdrawal of Russian forces.