That was my thinking as well.Random guess - Superman and Supergirl…
Plus Krypto!
It would be natural next step after her solo movie next year. I think it’s only reason Gunn was reluctant to say he was working on “Superman 2” . Meaning not direct a follow-up to events in the first movie. Superman is part of a bigger universe. If not Kara someone else in “family”. What if Luthor made a 2nd clone that is a teenager? Too soon for Superboy.
Gunn said he was not a fan of subtitles. Why he dropped Legacy from Superman. Also dropped Woman of Tomorrow from Supergirl. Which is fine for first film but what about sequels? I have this feeling he is trying to redefine how sequels are labeled and marketed. Even if it basically ends up being “Superman 2” anyways.