To see what I mean, imagine that tomorrow the Communist Party is dissolved, a new democratic constitution is installed, and following that, the country elects a true parliament and a new executive. Is it hard to believe that all of that will ever happen? Yes, it is very unlikely. But that would be but the very beginning of what is needed.
The next step would be for US to lift sanctions against Cuba. Legislation needs to be passed for that, and said legislation would be against the interests of people who used to have properties in Cuba before 1959.
Nationalized properties are not the only litigation targets over anything Cuban, because the government from 1959 to the date took a lot of loans that didn't repay. The international legal system would find ways to ask for that money back to any future government, corporation, or individual living in the island, which in turn would make the cost of living or doing business in Cuba extremely high, even in the absence of the Communist Party.