X-Men Everything We Learned from The Watch Party of DOFP
The Recent X-Men Days of Future Past Watch Party featuring Simon Kinberg (Writer of DOFP & director of X-Men Dark Phoenix) had a few interesting pieces of info.
Original Dark Phoenix Ideas
"It's possible that... in the alternate universe... because it would've been about ten, fifteen years since The Last Stand, you could do Dark Phoenix with Famke. And you could do it with the Hellfire Club, and you could do it I think with the screen time it necessitates because it's such a complex storyline. You'd probably want a two-part movie: you'd want to bring the Hellfire Club in; you'd want it to be truly intergalactic; you'd want to bring in Lilandra; you'd want to really tell it that way. And I think you'd need at least one bridge movie this [Days of Future Past] and the beginning of that [Dark Phoenix]. But the maturity of those actors and the history that goes back would've been 25 years - at this point (2014 when DoFP was released) 20 years since X1 - could've been really interesting."
Gambit Setup
"We had a tease of it at the end of Apocalypse. The Essex Corp is something that you see in a tag at the end of Apocalypse," Kinberg recently said during a watch party for IGN. "We had talked about doing something with him, and I won't get into the specifics of it since it's no longer a 20th Century Fox property and now it's part of the MCU. I have no idea what the plan is. But Mister Sinister was going to be part of the Gambit movie starring Channing Tatum."