Apple has released iChat Update 1.0 which “renews the .Mac certificate required by iChat for encrypting text, audio, and video conferences.”
According to Apple’s documentation, “This document will be updated as more information becomes available.”
Or, in other words, after Steve Jobs’s Macworld Expo keynote – hint, hint. Quick, somebody start digging through the code! 
iChat Update 1.0 is available via Software Update and also as standalone installers:
More info and download link for iChat Update 1.0 (PPC) – (2.3MB) here.
More info and download link for iChat Update 1.0 (Universal) – (3.9MB) here.
Related articles:
Analyst: Apple working on second ‘iChat mobile’ cell phone – November 20, 2006
Cringely: Apple’s iTV strategy is iChat on steroids – September 22, 2006