One of the amazing things that happen in many time travel stories is that mistakes from the past can be erased. X-Men Days of Future Past is changing the future of X-Men films for the better. The movie is undoubtedly the best the X-Men franchise has ever offered and is going to be hard to top. One of the best things about Days of Future Past is that it corrects some grievous errors that took place in the third X-Men movie the Last Stand.
The Sentinels are no longer a threat
Wolverine was successful in helping Charles Xavier and Magneto change the past to alter the future. The biggest reality that changed is that the Sentinels are no longer a threat to the future and have been effectively stopped. The work in the past changed the entire timeline of the whole movie series. All of this means that the future X-Men movies have a clean slate to work with.
Characters killed in The Last Stand are now alive
Another story altering change is that the events of the last Stand seem to be reversed. At the end of the Days of the Future Past, Wolverine walks through Xavier’s School for Gifted Youngsters and all of the characters impacted by other X-Men films seem to be unchanged. Specifically, Jean Grey is alive again and the Phoenix seems to have never happened. Scott Summers was not killed by the Phoenix and is going to be available for future X-Men movies. Finally, Professor Charles Xavier is back at the helm of the school and the X-Men. Xavier was disintegrated by the Phoenix in the Last Stand.
Characters killed in Days of Future Past are alive
There were several of the main characters in the X-Men films that did were killed in the future. The successful mission to stop the creation of the Sentinels caused all of those events to no longer exist. Many of these characters were present at the school in the closing scene and seemingly unharmed. All of this allows these characters to be present in future installments of X-Men movies.
An alternate timeline has been created for the X-Men that will allow for even more creative story telling. One reality that was evident in the comic book version that may not be part of the movies was an unclear future. The comic version left the reality that the same future might still be possible if events started to shift in that direction again. The events of the future had been stopped for the moment but could deteriorate into the apocalyptic future the X-Men were working to avoid.