I'm sure the culture will survive and thrive and hopefully more of the beautiful architecture in Havana will be restored. I don't think that a few fast food restaurants will hurt the country, but other things are bound to change also. As the citizens hopefully become more prosperous, there will likely be fewer 1950s cars on the road...although they have become such an iconic symbol of Cuban tourism that I'm sure that some of them will be maintained as long as possible.