Random thought I had earlier today: So we just got done with 5 characters over the course of a year and now we move on to 6 characters over the course of two years. It makes me think that maybe Sakurai will do something just a tiny bit extra to make the wait easier.
I'm thinking something simple like two bonus echo fighters, one each year. My best guess would be that these would be echoes in the same vein as Dark Samus and Daisy, nearly or totally identical to their base fighter in terms of moves and stats but having modified animations. The two that come to mind as easiest to implement would be
Octolings
Gooigi
It's also entirely possible that one or two of the 6 newcomers will have an echo of themselves added with them. Getting the roster up from 88 total to the nice even 90 would be a great place to leave things once development ends. Then, when Switch 2 launches in 2023, Ultimate Deluxe will be a launch or first year title with an extra 10 fighters pushing the character select screen to the magical 100.
In any event, I can't shake the feeling that Sakurai will find a way to do something extra over the next two years cause he's kind of a masochist. I could be completely off base of course.
Anyway, if you had to pick just two more echo fighters to throw in before the end of Ultimate's lifespan, who would they be?