It'd be more likely that Arena would get an OVA. Main plot takes place pretty much over the course of a single day, after all.
In other news, we might Score Attack versions of characters as unlockables, like Unlimited mode in BlazBlue. Check out this screenshot:
Not even NaruKAMI can get that kind of damage with that kind of combo normally, and it isn't Golden Arena mode because the other character has a navigator and no skill icons have appeared. Score Attack characters have damage buffs that would explain the added damage neatly.