Let's not forget it was also other undesirable groups as well that were murdered. Gypsies, homosexuals, extreme religious people, Roma, Mentally disabled and Polish people randomly executed.
I give this 0% chance of spreading into NATO. Ukraine is easy pickings, NATO not so much. After Ukraine I could foresee moves toward the Baltic nations at the very most in the distant future.
In one way I'm glad my father isn't alive to see what's going on In Ukraine. He was a refuge who fled from the Russians in January of 1945 in Poland. He lived close to a sub-camp of Auchwitz and saw prisoners in a forced march. They fled Poland with the retreating German Army into Checkoslovakia and then into war ravaged Germany.