So assuming that Stalin dies of a heart attack 1-3 months before Barbarossa, and Molotov ends up being the top man, at least at first, I am wondering what consequences that might plausibly have on WW2 and Soviet politics.
Some thoughts and questions on this:
1) Stalin was highly ideological in his outlook, and this heavily influenced the decisions he took during WW2 (as well as his decisions before and after the war). So to what degree did Molotov share Stalin's ideological outlook? Did he believe as deeply as Stalin that Imperialism would mean that non-Socialist powers would naturally be drawn into conflict with each-other?
2) The Soviets were receiving more and more intel saying that the Germans were going to attack them - but they'd known that Hitler wanted to attack them since Mein Kampf came out, and intel giving previous dates for Barbarossa had been and gone already, so while the Soviets knew the attack was coming, the case for an attack coming soon was not so clear as it seems from hindsight. But still, war was clearly coming, and Molotov is a different character than Stalin. So how might he respond to the intel?
3) Every Soviet succession resulted in a power struggle and purges. Whether they were the bloody purges of Stalin, as he eliminated every possible competitor for Lenin's crown, or the mass firings and demotions Brezhnev instituted when he took over from Khrushchev, followed by Brezhnev's power struggle with Kosygin and Podgorny to collect the reins of power. Does the expectation of German invasion (Stalin seems to have expected war within 2 years of 1940), mean there is no purge and power struggle, or does it merely mean that it is shorter and more intense?
4) Can Molotov keep the top job? I suspect that Beria would be an especial threat, but then, maybe Beria isn't important enough at this point to be a player for power.
5) Molotov lived a long time in OTL - he died in 1986 at the ripe old age of 96. Potentially, the Soviet Union could be ruled by him for the next 45 years. Considering it is almost inevitable that he (assuming he isn't purged in the first months after Stalin's death) he will have a cult of personality built around him as the Soviet wartime leader, I imagine that the Soviet Union could be quite different than our Soviet Union in 1986.
fasquardon