>>538157896
Its a collab with date a live V, the explicit mentioning of season 5 basically gives a high chance for Mio, as that would be their only possibility to add her but then again Mio would be downgraded powerwise if she was an SSR, lorewise UR would definitely make more sense.
If they'd add a new DaL collab then you can always add the standard girls like kotori,natsumi, yamais, but for Mio its now or never.