I could see that being an issue with the original ride, but I don’t think it was the kind of thing that would limit the entire franchise. There’s already a pretty high suspension of disbelief the minute you enter the gates of any theme park- the specific Back to the Future dates would actually be pretty tame compared to the storylines of most other rides. Again, it’s likely not happening, but I still feel like Universal parks were better with that property as a headline attraction.