So I don't think anybody is anywhere near ready to concede. It's certainly going much worse for Russia than they expected, but being where we're at today is also far from what the US had in mind 9 months ago when this all started. It seems the most likely outcome for this war is a long, bloody, and expensive affair. The real issue is the specter of WW3 in the backdrop. There's an argument to be made that Zelensky sees that as a win condition (as per the topic of this thread), but fortunately it seems that neither the US nor Russia do. And they are the ones that get to decide if/when that happens.
Giving in to the nuclear and other blackmail that Russia uses will never get lasting peace.
All it will do is get Russia to invade again in the future. You only need to see, Moldova, Georgia, Crimea, and Donbas to see this.
The only real peace for this war is a peace where Russia retreats entirely from Ukraine, militarily defeated and it becomes clear to Russia that any future invasion will be met with an even stronger force.
Otherwise the little green men will keep appearing and the Russians will keep invading countries.
But nobody wants to concede anything. So the war will continue, undoubtedly with plentiful more opportunities to find ourselves in WW3.