This seems unlikely to me. If Ukraine joins NATO while they are still at war with Russia, then article 5 gets invoked immediately upon their admission. This means there’s no way NATO will choose to admit Ukraine until the conflict with Russia has ended. Putin knows this, so he is incentivized to not end the conflict. He does not have to conquer Ukraine, and does not have to maintain a high intensity conflict - just enough conflict so that a few soldiers die here and there on both sides on a regular basis. A bit of a squabble. More of a tiff, really. It wouldn’t be any kind of attempt at victory, just long-term maintenance to keep Ukraine from joining NATO. Russia can sustain that low level of conflict for an awful long time, I’m sure. I think the only way out of this is ratcheting up sanctions until the Russian populace is so miserable that civil unrest becomes a major concern for Putin.