Well Messenger already has Yahoo integrated into it and they have a beta version that has gtalk working. They have said they are going to try and get aim/icq also working as well so in the future I think that we will have multi-protocol officially on messenger.
quote:
In a presentation to the Georgia Institute of Technology's IEEE Student Branch, Microsoft employee Andrew Jenks reported that the Messenger team had been working on multi-person audio/video chat, and they are also attempting to create interoperability with AIM/XMPP/ICQ users like the way Yahoo! Messenger works now; there is a basic internal version that works with Jabber already.[28] However, these features were not seen in any of the beta versions of Windows Live Messenger 2009 as of the latest release, Milestone 3.
Microsoft sent an invitation to participate in the Windows Live Messenger "9" beta program to Microsoft Connect members on November 20, 2007; a week later, Microsoft began sending out emails welcoming them to the Windows Live Messenger "9" beta program for the first release, known as Beta 0.
Also see my other post I made here
http://forum.mess.be/index.php?showtopic=24278&pi...art=0&#entry175891
It is possible for an addon to integrate other protocols it has been done in the past.