I Just felt for writing this now....

My theory about the very last Fantastic Beast movie: We will meet Luna Lovegood before or after her hogwarts years. I think it could be possible since Newt is her grandfather-in-law.  Maybe Newt want to make sure the magical beast will be taken care of in the future too after Newt die because Newt is at the time Luna live old?  Newt end up as a kind of "teacher" for Luna, almost the same as Albus Dumbledore was for Harry.... And this is why Luna end up working as a magizoologist too... because of all the stuff Newt have told and teach her and she felt sad if the beast not have proper rights. She make a promise with Newt about to protect and care for the beast too and make sure they will be taken care of after Newts dead.

I think it could be fun. I hope Luna do a "comeback" in a fantastic beast movie.