We have 1 DLC slot left for Smash Ultimate and people's hopes and dreams were already started to be crushed by Dante being a Mii.

I only see 3 real options left here...

- Baloon Fighter, an old Nintendo IP.
- Doomguy, because he been ported to the Switch and he has lots of legacy.
- Reimu from Touhou. Japanese and popular, plus lots of good music.

Personally, I see Doomguy going in. The char is big and you have a big company behind him. Yeah, the game is gory but you are not porting the demons, just the guy. As long as he doesn't GUTS AND GORE anyone he would fit just fine. Plus the BGF 9000 would make up for a nice ultimate.

Of course, Nintendo may pick another jRPG character with a sword. We don't have enough of those...