I thought Bungie weren't going to have any DLC for Reach.
They don't want to split the community with map packs, like what happened with Halo 3. New maps can be supplied via Forge, and easily rotated into match making for everyone. The fact that ODST came with all the maps, seemed like an attempt to try and standardise the map set across Halo 3's multiplayer. Why would they split the Reach users when they have this amazing tool that can provide infinite map variations? I'm pretty sure any maps they did release via DLC would be replicated by forgers pretty quickly, with the new phasing physics, it's a lot easier than in Halo 3.
The "definitive Halo game". Not the "definitive Halo game, providing you buy new maps further down the line".