Supposedly Microsoft is working on a Google Chrome OS counter. This could be the Gazelle browser, which wants to treat the browser itself more like an OS. The Gazelle prototype supposedly will to do things like protect webapps from each other, and isolate different browser tabs (like Google Chrome does and Firefox is going to do).
It’s just one of many research projects Microsoft is working on, but it would make sense for them to unveil this one next week, to show that they’re not taking a backseat to Google. It won’t replace IE, at least not for awhile.