But while WW2 was diasterious in term of human life lost for USSR, the positives are there, they gained new territory in the baltics and installed Communist puppet regimes all over Eastern Europe. Stalin also became a war hero for leading the USSR to defeating the nazis, without WW2 is Stalin ever seen in such a bright light? Does he stay in power aslong without WW2 boosting his cult of personality?
Honestly, I think all of these "positives" were long-term negatives.
The WarPac was a burden and if the system the USSR developed was an ill-fit for it, it was an even worse fit for other countries resulting in an erosion of political credibility in the USSR as satellites either did better or worse than the USSR.
Stalin being a "war-hero" is also an overall negative in my view since it tangles the legacy of Stalin with the legacy of the heroic struggle against German invasion... And to fight WW2, Stalin's cult of personality was greatly intensified.
The wars against Finland and the Baltics, direct reactions to German expansionism, made the world less safe for the Soviet Union in the long term and maybe even the short term (I think the Soviets would have done better in Barbarossa if Germany had started closer to Moscow but the Soviets had started on the Stalin Line fortifications but I could easily be wrong about that) even in a world where Germany DID invade.
And finally, WW2 confirmed for Stalin the crackpot Marxist theories that led Stalin to behave so provocatively after WW2 and started the cold war (since Capitalists inevitably must fall to infighting as in WW1 and WW2, Stalin was expecting WW3 between the US and UK imminently).
The Soviet Union is a much, much happier place without WW2 and much stronger and more prosperous. And yes, I think the Soviet regime could survive to the modern day. Though as with China OTL, we may not like to call it "Communist" any more.
fasquardon