#Apocalypse is not an alien. :) #XMenApocalypse
— Bryan Singer (@BryanSinger) December 9, 2013
Not refuting the rest of the spoiler scene, it seems to suggest Apocalypse may be something connected to an overall theme that's either time travel related (*cough* past fall *cough*) or something else entirely that may have earthly ancient roots. KP will dive into this at a later date once the film has been released as a final product to better go over the possibilities of how it may all interconnect into a larger building picture including the potential for an Onslaught follow up after Apocalypse depending on the story path used. (Too much potential spoilage to go into it right now, but a heavy almost full white barred entry does sound like fun to post too...)
Also in other interesting tidbits. This image popped up over at Bleeding Cool which in turn is from Sci-Fi Now.
It depicts Wolverine with metal claws again in his future side costume. Suggesting the Days of Future Past timeline is alternate to the point that events from The Wolverine may not have happened or that in some event prior to the events of 2023(allegedly the future time of DOFP) but after the events of The Wolverine, he manages to get his metal claws back or repaired from where they were cut off. Rather makes sense that he would want them repaired to better handle sentinels though. I'm not sure how well bone would fair against their machinery and constant design improvements. It could very well be as simple as they were reattached off screen before he left Japan.
Overall, it's looking like Fox is starting to get their X-Men franchise building in a quite decent manner for the next decade with an amazing amount of potential and directions that can be taken and explored.