Just like with Fargo, fans will enjoy certain references to the source material, but inside knowledge of the X-Men lore won’t be required to get everything out of Legion’s future stories.
So if we’re to believe Noah Hawley’s recent comments to Blastr, Legion will continue to embrace aspects and elements of the X-Men lore as it progresses, but we shouldn’t expect any literal adaptations of X-Men stories.
Hawley seems to have an interest in using the fundamental DNA of the X-Men universe to tell a story that’s uniquely his own, and that’s something that fans have also gravitated towards.
While there’s going to be a concerted effort to “reward” fans who have a knowledge of the mutant world, we’re not going to see a small screen version of Days of Future Past play out anytime soon.