I've been using google talk for a while now. I use it so that I can talk to my friends hundreds of miles away for free. It's really nice, and seems to work well. All you need is an acount, and a 5 dollar mic, and a high speed internet connection and you are ready to go.
This rumor's been around for awhile. My bet is - if they do, it'll either be completely web-based (AJAX, Web2.0) or be a modified Linux. I hope they do come out with one - it'll be interesting to see.