In the X-Men comics Apocalypse selects and upgrades four powerful mutants to be his four horsemen. This is the group he has rampage across the world to test everyone's strength. The weak are eliminated and the strong are promoted.
In the after credit scene of X-Men Days of Future Past we see a young Apocalypse and a group of four horsemen rest upon a hill. These are his four horsemen of this past age. When Apocalypse wakens from stasis one of his first acts will be to recreate this group.
It sounds as though the Horsemen will be similar to both their comic and Biblical counter parts and be named after 4 primary disasters to befall the humanity they are War (Conquest in the Bible), Famine, Pestilence and Death. Apocalypse carefully selects each of his riders amongst the powerful people (typically mutants) of each age, then uses technology to further enhance each one. Sometimes the rider wants to join with Apocalypse other times as in the case of Wolverine they are forced into it.
The recruiting and alteration of each Horsemen is said to be a major part of the film. Actor Oscar Isaac who plays Apocalypse revealed in an interview with IGN that:
"Without giving anything away, the recruitment of the Four Horsemen is very cool. It’s very interesting the way that he does that. You know the idea of – the way that cult leaders do – they find people that are in need of something and try to fulfill that thing in them – as it relates to every one of the Horseman.”
Who will each Horsemen be?
The Horseman of Death
One of the Horsemen is going to be Angel. This can be said with the utmost certainty as a picture of Ben Hardy has already been released depicting Angel as Archangel also known as the Apocalypses Rider of Death.
The Horseman of War
Wolverine in the comics was also converted into one of Apocalypse's riders and I think he could find himself used in that way in the film. Wolverines Adamantium claws were cut off in the film the Wolverine but then were shown covered in metal during the future sequences of Days of Future Past. How does he have his metal claws in the future? This seems to point toward something happening in the interim that would recreate his metal claws. Certainly, one character capable of repeating the Weapon X Skeleton process on Wolverine is Apocalypse. With that in mind I think Wolverine would make a very good rider for War.
I don't have any other great insights on the other Horseman, I think the two mutants selected by Apocalypse in the comics in the initial series make sense.
My guesses for the Horsemen
- Death - Angel
- Pestilence -Plague a member of the Morlocks has the power of taking diseases altering them and making them more lethal
- Famine -Autumn Rolfson - a mutant girl with power of turning organic matter to dust
- War - Wolverine
Another Morlock by the name Caliban has also served as both Death and Pestilence. He had the power of tracking other mutants.
There was a mutant cyborg named Ahab who became Famine during the 12 Storyline.
X-Men Movie Hub
SPOILERS - Explanation of After Credit Scene in X-Men Days of Future Past
First concept art from X-Men Apocalypse
How is Apocalypse defeated and killed