This is why I think another free update dedicated to her would be good. Tabata makes it seem like shes not exactly DLC (never specifically saying that she is going to be DLC) and also makes mention of the next content update being something "happy" or "making the player smile". I don't see how Ardyn will do that, yet we know he is the next offiial DLC.
Plus, relegating her to DLC only may insult the fanbase more since Luna has been one of the largest controversial parts of this game. A free update allows everyone to play with her and solve the problem while giving them good recognition.
I dunno now I'm probably getting too much into tinfoil hat territory, but I'd much rather Luna be free, just Character switch And Chapter 13 v2 were free (and they were pretty major)