Ideally every sequel will be better than the original. What I said was that BotW could be invalidated by a good sequel, as in, there would be very little reason to revisit it since the sequel is better in almost every way. There are still lots of reasons to revisit Mario 64 and the original SMB - their tight controls, fantastic level design, iconic music and colorful visuals hold up well to this day. If BotW 2 leaves everything but the art direction and climbing system behind, very little of value will be lost.
What about Metroid? It was completely invalidated by Super Metroid.
And I do think that BotW will stand the test of time despite the potential of it's sequel.