Well, nothing stops someone from doing that today, except for MUD, which would exist even if Russia finished off Ukraine. NATO’s ‘line in the sand’ is behind Ukraine, and not in front of it.
Of course but they can get all the countries that are not part of NATO, wait a few years and then come back with full strength, new ressources, new alliances and then we can ask ourselfs if there was not a place in time we could have prevented this…
Also I don’t like the current course of the NATO that much. I’m all in for deescalation but at some point and after all the threats from Russia I really wish the NATO would step up and say, we don’t want any encounters with Russia but if they choose to declare one of our allies as “war party” because of their support to Ukraine, we are behind and will defend them. I think this also would give some countries more confidence in supporting Ukraine with better weapons and supplies and show Russia that we mean business.