@Behemoth.Ravenlord I obviously wouldn’t know more then anyone else. But just to play speculation on the live action films if not DCEU movies…
Supergirl and the first two Nolan films were on this series at launch (Supergirl despite being announced to be on at launch was a few weeks later if I remember but basically at launch). So I would say those would be the most likely since they were on here before, maybe they will not inclue all three Nolan films. Not as likely as Supergirl, but not impossible for sure.
As far as what else it could be, just going off the top of my head the other live action pre-DCEU movies I can think of include Green Lantern, Superman Returns (which would be a good companion to the other Superman films on here), Jonah Hex, Steel, Catwoman, Watchman, and Constantine. I believe Warner owns the rights to all of them but haven’t looked it up, but I did before and going off memory I think all were either made after Warner bought DC or Warner has since owned the distribution on.
As far as movies with DC characters Warner doesn’t own the distribution on the 2 Swamp Thing movies and the 60’s Batman movie I think all three are not owned by Warner, so not impossible but highly unlikely.
Also worth mentioning that most of the non-superhero movies based on Vertigo and other imprints such as A History of Violence, Road to Perdition, etc are in most cases not currently streaming somewhere else that I have seen and owned by Warner. Seems unlikely they will be on here but not impossible I mean technically Road to Perdition and a history of violence are the only DC films to be nominated for academy awards, the former even won one for cinematography.
I may have missed some, and honestly would not be surprised if they are not just putting Supergirl back on here (although wouldn’t complain about that, I didn’t get around to watching it when it was on here before) but I would guess it would be at least one of these movies.
I do like they said some favorites coming back after a sabatical, but not that they all were. Hope it means something new to the service even if just a Dc Animated film. Ready for some new blood to be rotated in as it was.