First of all, where is NATO going to get 50,000 troops? I will assume that you are talking about Europe and Canada because the U.S.> government will never allow military boots on he ground in Europe.
Also consider that one of the reasons tht we have this war is that some idiot offered to make Ukraine a member of NATO even though it does ot have any land on the North Atlantic.
Any move of troops against Russia would be the end of the EU. The end of Germany's government and any other country that is depending on Russia for gas an oil or has a border with Russia. Believe me, but Putin still has the power and troops to respond to the NATO threat in force.