Microsoft’s dropped a ton of new information on Halo 4 via the retailer-focused ExpertZone portal, including confirmation of new weapons and vehicles.
As per this OXM piece, the game will contain 10 new weapons, including the Forerunner Scattershot rifle, the Remote Projectile Detonator and the Rail Gun.
Halo 4 will include 10 multiplayer maps at launch. The only two we know about right now are Wraparound and Warhouse. Others will be released as DLC.
In addition, the episodic Spartan Ops campaign will last 12 “incremental” hours, apparently, in either co-op or single player.
Two new vehicles will also be included.