The real effect will be on the Cuba people themselves. Since the fall of the Soviet Union the economy of Cuba has been supported by massive non-American tourism and petroleum supports from Hugo Chavez and investment from many unnamed companies who wish to avoid being caught under American commercial bans on Cuba. The likelihood of a large change right now is slim, as Castro will still have a large hand in the policy of Cuba while his brother Raul Castro deals with the continuing embargo and loads of tourists coming to the country. Many prospects of change have already started, as some restrictions on owning property have been weakened in the last 7 years. Foreign companies who wish to buy up anything from this tourist paradise have been able to in recent years as long as the Cuban government or citizens share 50% or more of the property. Cuban exports of sugar and tobacco products have found a place in Europe and abroad, and with the open market policies with other communist nations such as China, the restrictions on Cuba are not finding complete support as they once did in the past. The exception is of course the few interest groups who have direct ties to Cuba itself, who are not likely to forget Castro after only one or two generations living outside Cuba.
The expectation of quick change after Castro dies avoids recognition of the slow change that has taken place in Cuba since 1991. For the most part Cuba's change is inevitable with Castro or without him. The Cuban government in reality has gained a lot of strength in the last 15 years and quick change will most likely come about if the Castro's decide it, or if a new JFK happens to take great interest in Cuba and its future.