Legion Season 2 wont receive an assist from The X-Men. The FX mutant series will remain separate from the larger X-Men movie continuity in Season 1 and beyond (renewal permitting), EP Lauren Shuler Donner confirms to IGN:
IGN: What do you consider the mystery or the forward momentum of this season? Is it finding out who his father is?
Donner: Probably the driving mystery is, yes, who is David? But not in that sense. It’s more, “Is David schizophrenic? Is he crazy? Or does he have powers?” That is the mystery. “Who is David?” We just don’t want to get into the Xavier world, because that’s not what this show is about.
IGN: What are the challenges in having this other, larger X-Men franchise? Will this be within that universe, or are you making it separate?
Donner: No, we’re making it separate. We’re our own world.
IGN: So even if it touches upon Xavier later, it’s not the Patrick Stewart and James McAvoy versions?
Donner: Yes, we’re in a different world. Exactly.
Stay tuned as we continue to monitor the cancel/renew status of Legion Season 2…