Skype is already a massively popular voice and video communication service with more 170 million users around the world. Microsoft plans to implement Skype in Xbox 360 with Kinect, Windows Phone, and other Windows devices as well as continue to invest and support Skype on other non-Microsoft platforms.
No date was given as to when Skype will appear on Xbox 360, but later this year (2011) is a safe bet. Expect more information to come out of the E3 '11 show in June.
You can see the full press release here - Microsoft to Acquire Skype Press Release.