I think that the normalization of relations with Cuba would end up being a non event.
In 10 years it would be a resort and the politics, while probably never being a western republic, would just evolve into the same thing governments are pretty much everywhere.
The Castro bunch is old and tired and the people have had enough of living in poverty.
Allow a bit of a standard of living to take root down there and it would probably be about as stable as any place in the western hemisphere.
Basically, it would just turn into an extension of the Florida Keys,...which is more or less what it was once upon a time.
