They can't make carol gay after all these years desu. She's a confident enough woman to have been out all the time.
Though I do have an idea.... it involves the part of carol that rogue took which was trapped inside her mind. I know kelly mentioned offhandedly that carol has those memories, but someone could do a proper arc to bring that carol back, join her with our carol and reveal that she's bisexual, just the woman loving part of her was removed.
Or alternatively, you could say that since she got mar-vells memories in her genetically, she does have an attraction to women because of it.