I feel like pedigree and a tad of curiosity/gimmick-novelty alone will prop up ARMS. Unlike most traditional fighters, there's a very easy splashdown point for younger audiences or parents or just more casual players to go in and "flail" or the less competitive modes like basketball and volleyball, there's enough meat to the bone for more than just the usual fighter demographics (even though the game itself does come off as a thin around the core with its more straightforward single-player offerings).
Here I am speaking strictly for Japan, in the west this will still be a factor but as you say fighters in general are trending on healthier numbers.
I don't think its going to go gangbusters out of the door if even ever, but the team pedigree will beget a pretty healthy marketing budget which should keep it from "bomb" territory just on sheer exposure-v-probability of sales conversion.
I suspect, westwardly speaking, that ARMS will see some knocks on it from the thinner single-player offering, especially when compared to peers like Injustice 2 or MKXL. Certainly, it will probably look good compared to SFV but then a polished slab of metal would also look good compared to SFV.