Would've been the end for the Russians as a nation. Hitler wanted to kill like 90% of the population, enslave the rest and use the Western half of Russia for lebensraum.
So the Russians had no other choice, than to fight to the end. Hence they also lost 26 mio people in the war, by far the largest of any nation.
Crazy thing is Hitler could actually have succeeded in this if he had treated the Ukrainians better at the start of Operation Barbarossa, most of them hated Stalin and his communist regime and were seeing the Germans as liberators to begin with. But as he (Hitler) saw them as subhumans he of course didn't even consider this option. So he turned a potential ally into enemies and partisans he had to fight while waging war in the East.
Thats what you get when you fight a war of extermination.