i dunno if they will, the weekly updates suggest theres a hell of a lot of polish and balance going into every multiplayer map to ensure the best experience. I dont know if Bungie will want maps people have created in 5 minutes cheapening the online experience. I dont want them there to be honest, PC is one thing because you have the tools to create maps that can live up to the level of the professionals, but i find it hard to believe that a similar feat will be possible on Xbox.
I think there will be official maps, and downloadable maps and that'll be it.