With Microsoft's acquirement of Skype, there was no longer any need for Microsoft's proprietary instant messaging service Windows Messenger Live.
Back in November 2012, Microsoft confirmed that after over 13 years of service, Windows Messenger Live was to be canned in favor of the more popular video chat service.
Microsoft recently sent out an email to Messenger users that the service will be shutting down on Mar. 15th, sans China (presumably because the IM service is still very popular there.) Microsoft has encouraged all Messenger users to move over to Skype.
However, this simply means that the Messenger service itself will no longer connect to the network. However, Messenger users will still be able to log in using Skype via their Messenger login details. XMPP support will be shutting off in Oct. 2013 and the final death knell for Messenger won't ring until Mar. 2014, when the network will actually be shut off.