I agree completely the family aspect is probably a big part of it. It also impresses me how the ride can work even for kids who have never seen ET. I think ET has a very good chance of survival, if however it was based on a more relevant kid friendly IP it's survival would be nearly guaranteed.
Problem with ET, outside of need of refurb, is placement. It can transition to have an entry into Hollywood/Central Park but it takes a big chunk of where Nintendo is gonna go. Universal's problem is already lack of empty space, so do they take over ET for the bigger IP or utilize the little bare land they have left on the MIB plot and restrict themselves from future park expansion?
Another question is whether the cost of a major refurb to ET outweighs the cost of adding Nintendo IP ride?