I don't know if I would call it "likely" at this point, but the above scenario is certainly possible...and that bothers me for several reasons.
First, I don't think Putin's thuggery should be rewarded, and ceding Crimea to him, and acknowledging the eastern provinces as independent, would effectively do just that. (It would be like letting a bank robber who's killed people during the robbery keep the loot he stole.) It would send a terrible message to the world's autocrats and dictators.
The second problem such a solution would present is: What does the West do about the sanctions it imposed? Discontinue them? Keep them in place? At what point would this conflict Putin started be considered ended?
Thirdly, how can Putin be held accountable if the war ends in such a manner? And who will be responsible for rebuilding the cities the Russians have destroyed?
Putin needs to be driven out of Ukraine, then charged, tried, convicted, and condemned as a war criminal. He needs to be permanently ostracized from the community of nations. Russia, as a country, needs to pay for what it did to Ukraine. I realize that's an unlikely, best-case scenario...but anything less will leave a very bitter taste in my mouth.