Halo 5: The latest....

a 20+ hour campaign.
Free dlc. (heard/read that somewhere at least)
Warzone, which seems to be the answer to firefight.
no veto/no vote --just straight map rotation to prevent over playing the same one over and over
no BTB at launch, but they claim it will be added later

I think it's officially time to start playing my copy of MCC again to get into the Halo 5 mindset for 10/27.

Edit:

Found it...
15 new FREE DLC multiplayer maps added to the game by June 16th 2016, in addition to the 20 that will debut with the game at launch.

http://www.forbes.com/sites/insertcoin/2015/06/11/343s-halo-5-apology-tour-free-dlc-maps-free-co-op/

Niiice. 20 maps at launch, not bad at all. Me and the wife are just finishing up our playthrough of the series (over halfway through Halo 4 now). Just in time for 5.

I need to just finish ODST and ill be done with MCC