Firstly, your comparison of Ayn Rand, a deceased novelist, to multi-decade tyrannical dynasties, is more than a little unhinged.
Secondly, the way that people act is strongly influenced by their surroundings, institutions, and social context. To think otherwise is the Fundamental Attribution Error. Castro and Kim don't have some special quality that would make them totalitarian dictators in the future;
Maybe the core difference is that Ayn Rand was under a lot less enviromental pressure to did what she did than those other people.
This month's media thread includes a short article on some people's idea to have Ayn Rand frozen, which ultimately didn't happen. My first reaction was a shudder. I thought, I definitely wouldn't want Ayn Rand preserved forever. My second thought was, What right do I have to say who can and who can't get frozen?
Whatever your thoughts on Ayn Rand, I think this can spark an interesting conversation: What, if anything, should humankind do about people who are widely seen as harmful for the whole? For example, if the Castro dynasty in Cuba or the Kim dynasty in North Korea decide to freeze themselves to ensure they will continue oppressing their countries forever, should that be prevented? (And yes, my opinion of Ayn Rand is such that these examples came to mind.)