In a Community Update at Halo Waypoint, 343 Industries gave a detailed rundown of all the new content that would be released for Halo 5 in December.
Notably absent from the list are any new gametypes for Arena.
At launch, Halo 5 included only four Arena gametypes:
The biggest Forge yet (which was built on years of community feedback) is making its debut to Halo 5, giving this next Halo 5 update its holiday-appropriate name. The new Forge includes a ton of new features including 1700+ objects, new object types such as FX and sound emitters, decals, invisible blockers, projected terrain pieces, lighting objects, a new multi-selection control scheme, precision editing, object grouping, true budget system (with a higher object placement count), smart magnets, and plenty, plenty more.
By contract, Halo 4 launched with nine gametypes in 2012: Slayer, Regicide, Capture the Flag, Dominion, Flood, Extraction, King of the Hill, Oddball, and Grifball. Tenth and eleventh gametypes, Ricochet and Race, were added in 2013.
With the lack of any new gametypes in the December update, this means that Halo 5 will still have only four playable Arena gametypes through the new year. January 2016 is the earliest any new gametypes, including Grifball, will appear in Halo 5. This also means that, when Forge is made available, Cartographers will only have four gametypes to work with.
Halo 5 currently does not include many popular gametypes that have appeared in previous Halo titles, including:
Halo 5 Grifball is currently in development and will be released some time before June 2016, when 343’s guaranteed free content support for Halo 5 will end.