Whatever the outcome of the war in Ukraine Russia will be left severely weakened (both militarily and economically), it will also see its global influence diminished, although it will still present a global security threat to NATO and the U.S.I don't see any danger whatsoever of Putin invading a NATO country. Unless Trump wins. Then, NATO could very well be shown up for what it is threatening to become: a paper tiger that gives a pretense of American hegemony. If Trump gets in, and Putin attacks, it's game over for American leadership. Forever.
In relation to future attacks against Eastern NATO states, I think the danger will not be a conventional military threat but rather non-conventional. Putin would likely use methods such as cyber attacks, disinformation, sabotage and infiltration of government to attack NATO states. Therefore the strategy of Europe and NATO should be one of preparedness and containment of Russia.