As with past updates, the content will be revealed over a number of days. The initial blast included the revelation that eighteen new hats--including a cowboy hat for the Engineer and a Russian ushanka for the Heavy--will be added to the title, in addition to a new community map. nope The community map, Arena Offblast, is described as a "fast-paced, high-altitude community map set in a top secret missile silo wedged into the top of a hollowed-out mountain."
Several hilarious hidden pages on the teaser site also hint at unannounced features. Any guesses, readers?
No release date for the update was announced. Thanks to Gummy Joe for the tip.