2. Young Xavier Will Die And The Entire Timeline Will Change
While not a result of the time traveling in Days of Future Past, the storyline Legion Quest sent a group of time traveling Mutants, including Bishop, back to the 1960s stop a rogue mutant (Legion, son of Professor X) from killing his father. They fail, Professor X dies and as a result, among other things, Apocalypse takes over North America several decades earlier than he had planned and the epic 90s alternate reality of Age of Apocalypse was born. While it is doubtful that Fox will be following this storyline to the letter, making a drastic change like that-even mid-movie would help set up the coming X-Men: Apocalypse movie as well as allowing for certain continuity changes to be made...