In "My Great Predecessors Part II" Kasparov mentions that the winner was to play Alekhine and in "Botvinnik's Best Games vol I 1925-1941" Botvinnik writes about it himself, though both accounts differ in the details. Kasparov goes on to indicate that Keres was offered a match subsequently in 1943, but declined.

According to Botvinnik there had been negotiations and an agreement for a match between Alekhine and himself in 1939 but after the Soviet Ch in 1940 and his poor showing, his backers (read Soviet Gov) decided to have a match between the 6 most recent Soviet Champions to decide who would earn the right. It was shortly after the match tournament that Nazi Germany and the Soviets had a falling out - they had been allies prior to the '39 invasion of Poland and dissolved the alliance in 1941.

I may not play well but I love history.

Regards