I think 343 is doing a pretty good job of consistent updates; HOWEVER, I think they REALLY need to embrace the Forge community. The very fact that all Halo: CE maps have been remade in Forge (with variations here and there) and the other Halo maps are also getting working remakes means that there needs to be a team at 343 whose job is to approve with quality control community made maps to greatly expand the map count. Some Forge maps are extremely insane, and the community should be rewarded for it. Even the unique maps are really awesome (Andy's Dorm, for instance).
I can't imagine a Halo 5 where Duck Hunt, Team Sumo, Infection, Griffball, and other wacky game types are present. That would be too much awesome for me to handle, so why isn't it happening? Some of those the community can take on (Duck Hunt and Team Sumo have already been done).