Far Cry 4 will have multiplayer in the map editor.
In an interview i heard that you could create singleplayer AND multiplayer maps. But recently some people got their hands on the map editor at some event. And when they opened the editor they could only choose between different singleplayer mission creators. So my thoughts are that Ubisoft let them out until the full game is released. So that they could only check out the singleplayer and not immediately the multiplayer.
I'm not really sure if my theory is right, but if it isn't then Ubisoft lost some braincells.
...
(Well. Atleast we can make cool singleplayer maps now!) :p