Could be wrong but... I'm sure they are going to do it via Dawn II. The last updates have been for RotZ, CoP, and ToAU fights. We've gotten Tenzen, Ouryu, Gessho, and the Mamool Wivre as well as the Zilart Bros. My thoughts on it is that we're going to see the final mission for CoP & ToAU redone in the next couple of months and then we're likely to see the Zilart Bros fight where you fight both at once, requiring both of their wins and possibly Dawn as well in order to do it similar to how the DMII fight was.

Seeing as they're redoing these old fights right now, it seems the most logical conclusion to think they'd update them via that fight, though I admit the fact this wasn't done with the DM Earrings may cast some doubt on this idea.