Welcome back, PB! And thanks for the thoughtful question.

I sort of asked the same question in a different way recently:

http://www.gangsterbb.net/threads/ubbthreads.php?ubb=showflat&Number=922682#Post922682

In my view, Michael knew, shortly after the Tahoe shooting, that all he'd get from Roth was a death certificate. So, his trip to Havana was to buy time to find out who the traitor was. "The rebels can win" may have contributed to his conclusion that he wouldn't be able to buy off Castro. But, by that time, it was really a delaying tactic to keep stringing Roth along. As I posted: the decisive factor may have been Roth's promising big chunks of his empire to others. In any event: Anyone who read the newspapers could figure out that Batista was governing on borrowed time.