A friend of mine recently found a video about the possibilities of Windows CE 7 that I think could be hint from MS telling what would be their next move regarding Tablets. Windows Mobile was like a skin running on top of Windows CE. That said, Microsoft can design, or anyone willing can, a wonderful skin to be used in Tablets. That skin or user interface, with Ink recognizer, ActiveSync and Office Mobile Support could become easily a very good opponent agains iOS and Android.
