“My guess is that both sides will tentatively agree to some de facto borders but not de jure borders. If it brings the fighting to an end, it would at least be a start.”
Not really, as it means that the war restarts in a few years, this time with Ukraine in NATO. If Putin has to settle for that short term outcome, he’ll have to first take Odessa, at least if he doesn’t want to see a firing squad in Moscow. So, probably another 2 months to 1 year of fighting, depending on how much support the US gives Ukraine.
War will not start again after AMERICAN outfits and personnel are stationed inside Ukraine.