Seeing how Halo will never fully go back to what it was. They can STILL easily provide everyone something to play and enjoy. So for starters, at the playlist level..
Ranked Playlist Group that is like Halo 2/3 (purely rank based, no exp)
Team Slayer
Team Objective
Team Hardcore
Team Doubles
Lone Wolves
Infinity Playlist Group that is everything from Reach and 4 (this will also be be area where you gain EXP and perks/ordnance)
Infinity Slayer
Infinity BTB
Infinity Objective
Infinity Doubles
Rumble Pit
Social Playlist Group
Team Swat
Team Action Sack
Multi-Team
....
I could write hundreds of other things but seeing how they ignore everything else there is really no reason to type everything up.
Ranked Playlist Group that is like Halo 2/3 (purely rank based, no exp)
Team Slayer
Team Objective
Team Hardcore
Team Doubles
Lone Wolves
Infinity Playlist Group that is everything from Reach and 4 (this will also be be area where you gain EXP and perks/ordnance)
Infinity Slayer
Infinity BTB
Infinity Objective
Infinity Doubles
Rumble Pit
Social Playlist Group
Team Swat
Team Action Sack
Multi-Team
....
I could write hundreds of other things but seeing how they ignore everything else there is really no reason to type everything up.