I'm currently watching a video of 13 minute gameplay of the new upcoming HALO: Campaign Evolved. Apart from the graphics, all the features shown in the gameplay can be traced up to HALO: Reach I believe. The things that weren't available back then in both Combat Evolved and Anniversary, are now integrated here. Like sprinting (controversial as it really changed the pacing of the game, especially multiplayer), and hijacking vehicles, at least these are the ones I've noticed so far.
But what excites me more, seeing that we don't have any HALO games here yet, maybe it might actually just be possible that when this new HALO: Campaign Evolved drops in the future, that game would also be released here on GOG? Or maybe the original versions instead. Whatever it is, I'm hopeful.