3) Magneto
When we last saw Magneto, he had seemingly embarked on a more heroic path. Many years have passed between the events of X-Men: Apocalypse and Logan of course, but it would still be very interesting if we were to find out more about what happened to the Master of Magnetism here.
The end of Days of Future Past certainly didn’t offer any hints, and with Charles Xavier set to play a key role in this movie, it could actually make a lot of sense for us to be informed about what his best friend and occasional enemy has been up to, even if he’s just referenced in some way.
It would, of course, also be nice to see Sir Ian McKellen make an actual physical appearance, and while it’s hard to say what sort of role he could end up playing in the story, here’s hoping he factors into it in some way, shape, or form.