I always have loved X-23 in her own right. I don't know that she would be creating a new franchise however, given that this is set in the future, while the rest of the X-Men universe is not.
I am not sure how they are spinning out the future of the X-Men, but this would seem to preclude an X-Men: Messiah/X-Men: Second Coming arc, which would have been a more natural way to go. OLD MAN LOGAN was more its own story, incapable of incorporating within the X-men as a whole, a sort of "what if" story. On the one hand, I love the trailer and the feel. IWorking in X-23 and including Xavier is a great workaround to not being able to use Hawkeye, Hulk, or Captain America, But they are burning a lot of bridges here.d