I would bet: Late 2010: FaceTime support on iPod Touch Early 2011: Support on new iPad revision WWDC 2011: 10.7 announced, support in iChat, API's available

I would bet: Late 2010: FaceTime support on iPod Touch Early 2011: Support on new iPad revision WWDC 2011: 10.7 announced, support in iChat, API's available Late 2011: Open specification released for 3rd parties.