Yes! Its not just a rumour.Microsoft (MSN) and Yahoo! messenger announced that thier respective IM services would be interOperbale from mid-2006.This means you will now be able to add your msn buddies into yahoo and vice-versa and also chat ,send enmoticons and view their online status.
However ,before you start popping open bottles,you should know that all this has been promised earlier by both companies and not much happened since.But as this being an official press statement made by both companies,we’re inclined to give them the benifit of doubt. and wait and watch.