During Microsoft's E3 2015 press event, the company showed off an extended gameplay sequence from Halo 5: Guardians. It showed the campaign for the first time from the percpective of Spartan Locke and Fireteam Osiris as they go after Master Chief and his Blue Team in four-player co-op action..
Here's what Microsoft has to say about Halo 5's campaign:
"The campaign in Halo 5: Guardians will feature seamless drop-in/out online cooperative gameplay on dedicated servers, enormous, complex levels designed to support more enemies and bigger firefights, enhanced immersive audio and sound, sophisticated teammate AI, and much more, all at 60 fps"
Halo 5: Guardians will be released on October 27, 2015. The company also showed off the game's new and huge Warzone multiplayer mode at E3 2015 as well.
Source: Xbox (YouTube)