Presume Stalin dies in 1946, and Khruschev or some other moderate leader (unlikely, but bear with me here) becomes the head of the Soviet Union. While he believes that capitalism is an inferior system, he thinks that it will eventually fall due to its own self-contradictions and there's no point trying to force the matter. The Soviet Armed Forces are reduced to a much more rational level, and more spending goes into consumer goods and recovery after the horrors of World War II.
After he dies in around 1970, he is succeeded by another young Khruschevite who continues relatively good relations with the West (no Brezhnev).
What would the effects of this be? Could the USSR eventually reform along the Chinese model and (eventually) democratise?