Stalin was a cautious, rational bastard. He wouldn’t start WWIII unless he thought he was going to win.
I’d say that but for our atomic bombs, the odds in Europe looked very much in favor of the Soviet conventional forces in 1945–1949. In fact, the odds in Europe still favored the Soviets after Stalin died but we breathed easier because Stalin’s successors were far more cautious than he ever was. The historical fact is that only one Soviet leader was enough of a cowboy to sign the original Nazi-Soviet non-ag pact and the Soviet leader was Stalin.