There are three IPs in Smash that need a net reduction in characters, regardless of the roster size of Smash 6.
Pokemon and Mario are huge, but they should shrink their fighter count.
Pokemon: Cut Pichu, Squirtle, Ivysaur, Lucario, Greninja, and Incineroar. Add a Gen 9 Pokemon. Maybe Gen 10 instead if Smash 6 is that far off. You could maybe even throw in a Pokemon from Gen 3, 5, 6, or 8. There are so many Pokemon that in the long-term they should have more of a rotating cast in Smash instead of having a lot of the fighters in 3 or more Smash titles.
Mario: Cut Piranha Plant and Dr. Mario. Add Waluigi (or if he still doesn't make it, Paper Mario or Captain Toad instead)
And Fire Emblem needs some cuts too because of how similar a lot of the fighters are and that it's a lot smaller than some other IPS in Smash.
Fire Emblem: Cut Ike, Lucina, Chrom, and Corrin. Make Roy an echo.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima