The problem right now is that there is no way NATO can admit Ukraine. It would be a death sentence. Putin will just invade again, and now the NATO countries would be put on the spot under Article V, which is not where many of them want to be. I would expect many of them would not send assistance, and NATO would fracture.
Maybe that's not the worst thing. I'd rather not have Hungary or Slovakia or other fascist-lite states in the alliance. But I have no idea how it would shake out. Zero visibility.
We are already having to deal with the Baltic state problem. Hopefully the EU member states would come to the defense of longstanding NATO members, as it's a different calculation than the country we literally just invaded. On the other hand, I'll bet sending French soldiers to fight on behalf of Estonia would be very unpopular and Le Pen would be very happy to see it. And the US would probably sit it out.