Smash 6 is probably going to take far longer to even become a thing due to the fact that Masahiro Sakurai has stated that he needs a break. He really does, to be honest. Not a one or two year break. He needs a lot more. I say that after FP2, we won't be seeing Super Smash Bros. for a long time.
On the other hand, there have been rumours that during talks for Square Enix reps, Geno was never considered, Sora was considered but negotiations broke down, and the only two characters who were seriously considered were Hero and Sephiroth, and this may have taken place as far back as 2017, just a year before Ultimate was announced and eventually released.