I completely agree that Spring Man has thus far been the posterboy for ARMS. This is why I wanted to clarify terms.
That said, I dont think being the posterboy for the first game necessarily means he is going to always be so.
The game's promotion, from Nintendo's point of view, has been modeled after Splatoon.
While Splatoon is not a character based game in the way that ARMS is, I would actually relate the characters on the cover of ARMS to the Squids on Splatoon. The first game had the orange girl and the blue boy. The second game wanted to show that it was the sequel by switching to a pink girl and green boy. As of right now, I'm inclined to think that ARMS 2 is going to have two other characters on the cover, possibly new characters or ones that are greatly altered.
I find this comparison much more congruent than that of Spring Man to Tracer. Nintendo has always created and followed its own trends, and I dont really see a reason to compare Spring Man to Tracer, with the exception that both games have gotten lots of DLC (albeit in very different ways, to the point that ARMS even stated it is done with DLC, similar to how Splatoon stated when it's DLC was done after the first game).
Let's leave that one for
@BluePikmin11 to come up with his famous out-of-the-box characters
I am still waiting for the amazing, Carmen Sandiego, to get into the game.
Or a frickin Oregon Pioneer. I want a Final Smash where you give someone dysentery and they are K.O'd.
(and to a lesser extent, am hoping for a TOMB RAIDER announcement with the release of the movie)/