The events of "X-Men: Days of Future Past" erased and altered the timeline of the film series, erasing the events of the 2000 movie "X-Men" and its sequels. However, speaking to Collider, director Bryan Singer reveals that the timeline is still not definitive and that the happy future seen in "Days of Future Past" can still be altered.

According to Singer, the ending of "Days of Future Past" was most likely going to turn out true given that Wolverine (Hugh Jackman) managed to go to the past, alter history, and make it back to the altered future. However, Singer explains that this is only the ideal future and that events in the present may alter this, preventing it from happening.

"The point is time's immutability. The idea that time is like a river. You can splash it and mess it up and throw rocks in it and shatter it but it eventually kind of coalesces," the director explained. "Any possibility could occur, but characters are still moving towards their immutable place."

This means that while anything can happen from "X-Men: Apocalypse" and its sequels the events of history will still try to make it so that the characters achieve the ending seen in "Days of Future Past," although the chaotic nature of time and history might cause rifts and alternate results. 

In regards to Hugh Jackman appearing as Wolverine, the director simply stated there has never been a film in the "X-Men" universe where Wolverine was not present. The character was not a main focal point but he did appear in a cameo role in "X-Men: First Class" and will likely do the same in "Apocalypse."

According to a separate report from Comic Book Movie is that Jackman's involvement will be revealed in the next trailer for the film, which is said to showcase Wolverine breaking out of the Weapon X program. 

"X-Men: Apocalypse" opens in theaters on May 27.