It is that simple. How might ww2 have played out if Stalin had died? Who would most likely take his place, how would they continue the war if at all? How might post war Europe look without Stalin?
Molotov was Stalin's favorite, although Beria may have the strongest position as the head of the KGB. The question may hinge on HOW Stalin dies--if Stalin knows his time is running out, he may force the politburo to accept Molotov, or perhaps Zhandov.
Intrigue within the Soviet Union, even during a war, isn't impossible to consider, and it is certainly possible that Stalin's enemies may have somehow engineered his removal from power. Given the situation at hand, the armed forces may have a critical role in such a move--at which point, we might see Volshirov come to power--although such a move would be dangerous in the extreme.
The question on the mind, though, is how the Soviet Union fares on the battlefield when top leadership suddenly collapses. While it would all but ASB to see the Soviet Union begin a civil war with German Troops on its homeland, the loss of a unified Soviet Command could be providential for the Wehrmacht. Atrocities commited by the Germans by this point guarantee that the Soviet Union will continue the war no matter the situation in the Kremlin, but HOW this is done is an open question.
Ultimately, the question of "How Stalin Dies" will change the course of the Soviet Union, and possibly the war. While 1944 is probably too late for the Germans to regain the initiative, it might be feasible for them to reach a sort of stalemate in the East.