Long Zheng reports that Microsoft posted a start menu concept as part of a feedback survey

Notably the Start pearl/button/orb rests in a curved corner that is darker to the rest of the taskbar which is now considerably more transparent and white. And quite possibly the taskbar is “double height” by default. Some applications in the start menu also have a cascade button on its right, leading me to believe its some sort of extended menu, for what purpose I don’t know.

Microsoft feedback survey: Windows 7 start menu (concept). Here, let me show you it