Multiplayer in MHWorld
In an interview, after the Sony's E3 conference, series producer Ryozo Tsujimoto was asked how multiplayer will work in Monster Hunter World. He stated that we will see more of the same from previous titles, but with interesting additions.
The game cam be played solo or with up to 3 other players. Players will be able to meet up in a "Hub" of some kind, before setting out on a quest. While venturing solo, you will be able to set off a "SOS Flare", as shown in the trailer, to signal for friends or other players to come to your aid.
This is the first time drop-in multiplayer will be in the Monster Hunter series. Also, it has been confirmed that Monster Hunter World will be cross region enabled for multiplayer, so no matter what region of the game you own, you can play with anyone in the world. But keep this in mind, Monster Hunter World will be exclusive to Playstation 4 in Japan, so Xbox One and PC players will not have "full" cross region multiplayer.
No other details have been given at this time.
Here is the interview with Ryozo, and MP discussion starts at 2:44.