Just read this from First Showing which supposedly are early details on how Apocalypse will make his appearance in the movies...it's a rumor but a spoilery one.
Not sure if I think this is 
or 
http://www.firstshowing.net/2013/exclusive-how-x-men-days-of-future-past-teases-x-men-apocalypse/
All right, so here we go. After speaking with an insider following the announcement of X-Men: Apocalypse, it was made apparent that they knew who was going to play the titular villain. More specifically, it was explained to me who becomes Apocalypse. Yes, an existing X-Men character will become possessed by the villain who can project his consciousness and powers into host bodies.
A second source gave us info from one of the most recent drafts of the script with the evidence. Supposedly, the final version of the script only changed one set piece (which has a surprise for fans) in the middle of the film from this draft, but that does not affect any of the details we've learned. Let it be known that we're not going to spoil the absolute end of the film because, truth be told, it's a pretty spectacular ending that has some tidbits in the future that you'll have to see to believe.
However, the credits bumper jumps back to the past with a young Erik Lehnsherr (Michael Fassbender) in a ramshackle house in the desert eating dinner, clearly on the run from all the authorities who want to bring him down. While using a well outside to get some water, the young Magneto sees something fall from the night sky and crash to Earth nearby. Upon inspecting the impact zone, he encounters what is described as an "alien form" who is "towering, terrifying, with a twisted metal face and dark pits for eyes." It's Apocalypse and he says, "I have crossed rivers of time to find you." Magneto asks, "Who are you?"
The alien responds, "I am your future." Suddenly Apocalypse merges with Magneto, who screams and blasts an insane amount of energy and shockwaves around him. This energy explosion levels everything around him, with a blast radius that goes for miles. As Magneto looks at what he's done, he has a realization of the power he now holds and a villainous grin begins to form before the film cuts to black.
All right, so here we go. After speaking with an insider following the announcement of X-Men: Apocalypse, it was made apparent that they knew who was going to play the titular villain. More specifically, it was explained to me who becomes Apocalypse. Yes, an existing X-Men character will become possessed by the villain who can project his consciousness and powers into host bodies.
A second source gave us info from one of the most recent drafts of the script with the evidence. Supposedly, the final version of the script only changed one set piece (which has a surprise for fans) in the middle of the film from this draft, but that does not affect any of the details we've learned. Let it be known that we're not going to spoil the absolute end of the film because, truth be told, it's a pretty spectacular ending that has some tidbits in the future that you'll have to see to believe.
However, the credits bumper jumps back to the past with a young Erik Lehnsherr (Michael Fassbender) in a ramshackle house in the desert eating dinner, clearly on the run from all the authorities who want to bring him down. While using a well outside to get some water, the young Magneto sees something fall from the night sky and crash to Earth nearby. Upon inspecting the impact zone, he encounters what is described as an "alien form" who is "towering, terrifying, with a twisted metal face and dark pits for eyes." It's Apocalypse and he says, "I have crossed rivers of time to find you." Magneto asks, "Who are you?"
The alien responds, "I am your future." Suddenly Apocalypse merges with Magneto, who screams and blasts an insane amount of energy and shockwaves around him. This energy explosion levels everything around him, with a blast radius that goes for miles. As Magneto looks at what he's done, he has a realization of the power he now holds and a villainous grin begins to form before the film cuts to black.
or 
