[Terminator-1000]

Taken from Gamespot.com

Gearbox's creative focus is on the multiplayer, and the developer plans to include new maps, and may also add weapons and vehicles. It makes sense to design new maps considering that the PC game will more often be played with larger numbers of players in a server. It's likely to support 32 players per server. Pitchford mused that it might be possible to release a mod pack that would allow fans to create new levels for Halo, but said it's too early to tell. For various reasons, it's unlikely that PC and Xbox players will ever face each other in the game

So its not for sure, its a maybe