Since the crossover is after the winter finales of all shows if they went with elseworlds versions of characters I'd think it more likely we'd see alternate versions of the regular heroes, not the new one. That way they can avoid mentioning any cliffhangers of individual shows, and set up Batwoman's Earth if she's on a separate one.
I don't think that will be the case though, and we'll just see the "real" versions of all characters.
Yes, it is possible this story might be focused on Batwoman with Elseworlds versions of the other characters but given that this crossover takes place in the established shows makes that device questionable as well. That said, the Elseworlds name is basically DCs "What If" series. Really, anything is possible for this crossover at this point. Although I do like the idea that it is meant to foreshadow the eventual Crisis that we know is coming.