tweeted that Invasion mode will be added to the Halo: Reach beta at "around 11am PDT" today.
Lest you forgot how Invasion mode works, it's a 6-on-6, Spartan vs. Elite gametype that sees the Elites on the offensive, trying to take objectives and unlock new sections of the map. The Spartans, obviously, have to defend said objectives. Also, unlike most other modes in Reach, Invasion allows players to respawn next to a designated teammate (out of combat), adding to the strategic possibilities. On paper, it sounds a bit like Bad Company 2's Rush mode. In the beta, Invasion can only be played on Boneyard, a new, huge map with lots of vehicles and progressively deadlier weaponry unlocked as the match plays on.
In other words, clear your schedule. You have plans tonight.