Back in 2012, when the Beast recklessly messed with the timeline to bring the original X-Men to the present day as part of some object lesson by Beast against Cyclops' actions both during Avengers vs. X-Men and in the time after that event, the original X-Men decided that it was important for them to remain in our present/their future.
Since then, they have each played major roles in X-Men universe, both in terms of character development but also in terms of actual direct impact on the world around them. They have fought back the desire to return to their own time, since they know that such a return to the past would require their memories to be wiped and they have so much more still to do in this timeline. However, the upcoming Extermination miniseries by writer Ed Brisson and artists Pepe Larraz and Marte Gracia revolves around the idea that they are now putting the world more at danger by remaining here than anything else.
That is the central idea behind the new piece of teaser art by Larraz and Gracia for the event that Marvel has released. It depicts Cyclops holding his visor, with the line, "Set it Right."
That is what will drive the original X-Men to return to their time. Extermination writer, Ed Brisson, recently told CBR, " I think it’s been understood for a while now that they need to go back to their own time. This story hammers home the how and why of it. We get into the implications of why them being here is a bad idea for the long term."
Whether all of the X-Men manage to survive their trip back to the past will be revealed when Extermination comes out, starting this August.