A lot of people don't know this but Disney have always had the toy rights to the X-men and Fantastic 4, (They just didn't have the film rights), meaning that they could have made Lego sets based on these already but didn't as Disney didn't want to promote something that they didn't fully own. Hence why we only got 2 Lego X-men sets and why they didn't appear in Lego Marvel Superheroes 2. But now Disney fully owns the X-men and Fantastic 4 expect to see Lego sets based on these characters in the future.