What storylines could be written in Middle earth?

With the success of Fantastic Beasts and where to find them I was wondering about possible prequels/conceptual storylines that could exist in Middle earth? In reading the books or researching the vast map of ME, what do you think are some possible characters or areas of the book that could be expanded on? Could you possibly build characters independent of the main book ones, or what characters in the Silmarillion/extra material have enough to build a film off of? Do you foresee future Tolkien films in the future?

The Children of Hurin and Lay of Luthein for sure. I could also see one detailing the Flight of the Noldor. As for if it will happen? No, not for a while at least. Christopher Tolkien refuses to sell the rights to any of these stories and he hated PJ’s adaptation of LotR. I expect that his children will be similarly draconian with the rights as well once Christopher passes away.