I love you all to death (Just so I can smash bros with you) (SSBWiiU/3DS)

[Kriven]

If this roster shows how big the final roster will be, at least, 51 characters in the game. Merely 12 more than the total amount of characters in Brawl...

That's about average for the franchise.

Either there's been a lot of cuts or the roster we're seeing does not show how big the final roster actually is.

Why? You already said there were 12 more slots than Brawl had total characters. That roster demonstrates enough capacity to bring back every single character from Brawl's 39, plus the six newcomers up on the site, plus six more newcomers if we assume there won't be a random and the Five won't be returning.