At the E3 press conference, Microsoft have announced details of Halo: The Master Chief Collection.
It will contain over 100 maps (that’s every map ever released) and Halo 1 through 4, including Halo 2, which will have the “full anniversary treatment”. You can switch between the new and old visuals at the touch of a button.
And yes, Halo 2’s multiplayer is there and intact.
It’s all happening on November 11th this year; 60fps, 1080p. The Halo 5 beta is included, and will be happening in December.