From the NYT:
MEXICO CITY — Fidel Castro stepped down Tuesday morning as the president of Cuba after a long illness. The announcement was made in a letter to the nation written by Mr. Castro and published early Tuesday morning on the Web site of Granma, the official publication of the Cuban Communist Party.
I’m no expert in Cuba, Cuban politics, or anything even slightly related to said subjects, but I am a pessimist, so I can safely suggest that Castro stepping down will change absolutely nothing. He says he plans to remain active in politics through his writings. Change is far more likely to occur once he keels over. His brother will likely stay in command, along with most of the ‘old guard’.