As pointed out by NoPyGod, http://msdn.microsoft.com/en-us/live//default.aspx states the following:
We recently announced that we’ll begin to encourage Messenger users to start using Skype. As a result, the Messenger developer program will end. Existing implementations that use Extensible Messaging and Presence Protocol (XMPP) will continue to work until October 2013. Existing implementations that use MSP will continue to work until March 2014.