With how stubborn Nintendo is on putting the MC/box cover face character of the franchises (hence how we got byleth instead of any of the beloved lords people actually wanted, and also how Terry got in instead of aaany of the SNK characters people were actually talking about), I think Springman HAS to be playable in some form. I don't think Nintendo will risk disappointing the MC/box cover character's fanbase over a specific character in the roster fans, they have been making it pretty clear with who they put from each represented game. I feel like it would be more of a "wtf" moment if people saw him being listed in that teaser list from March for NOTHING if he truly can't be upgraded (as people like to repeat saying), rather than not getting one of the others in the list (again this is simply based on the fact they have been putting the main face of a franchise every time, otherwise I wouldn't say this).
That said, I precisely expect a multiple alt situation because of such list. To be honest with you all, I feel like teasing a full list was a TERRIBLE idea. Usually we got ourselves to blame for setting our hopes on a certain character based on our own speculation, but here Nintendo has given us an official list to drool at / hope for. So no matter who gets in, the ones that don't get in will cause extra disappointment to such character's fanbase. I honestly think Nintendo should have never teased Arms in such way, unless it's a freaking alt costume scenario a la Hero. That's just how I see all this going to play, unless Nintendo decides to break their pattern of not including the box cover face / MC of a franchise.
My only other prediction is that, if for some dumb reason, they don't have Springman as playable at LEAST as an alt, and we get only ONE character from that list… then personally I think Min Min is what they will go with, for popularity reasons you all already know. That would be my personal non-springman prediction.
I love being wrong when it comes to Smash, so If I'm wrong with all this, then yay, because it means "anything can happen" gets stronger each time more, lol.