I really expected that he would, as he said in his resignation letter, remain president until his "last breath." But according to the Washington Post, Fidel Castro has resigned as Cuba's president.
Fidel Castro Stepping Down as Cuba's President
I don't expect this will change our diplomatic relations, or lack thereof, with Cuba, since in all likelihood his brother will now officially take his place...but one could hope. Jeffrey Dexter at U.S. Diplomacy seems to think so, calling Raul a "Cuban Gorbechev:
“Raul is also called ‘the practical Castro,’ and when and if he does succeed Fidel permanently, many Cuba watchers speculate that he’ll actually bring a less confrontational, more reform-minded rule to the communist island.