According to various news outlets, Bungie announced today, via their Facebook page, that the Halo: Reach multiplayer beta – of which Halo 3: ODST purchasers are automatically invited – is set for launch in January.
"Halo Reach beta coming in January so make sure you have your ODST copy's ready!", was posted by Bungie on Facebook according to IGN.
However, Bungie’s most recent post on the social networking site states: “Don't believe what you read on the Internet (unless it's on Bungie.net). No Reach beta in January.”
Whether Bungie is simply doing a little bit of clean-up, adding to the mystery, or simply stating the truth is unknown, but feel free to speculate.