I know everyone thinks an ARMS character is a given, but we may not get one until DLC. Or maybe we'll only get an Assist Trophy. ARMS is in the same situation as the first Splatoon game back when Smash 4 was coming out. So I don't know.
However it hurts to know that if we do get a character it will be Spring Man or, if we get lucky, Ribbon Girl. The rest of the cast is so much better. Min Min, Master Mummy, Mechanica, Max Brass or Dr. Coyle would be so much better. The only one who has a slight chance of making it is Twintelle.