Details about Photon (the codename for Windows Mobile 7 which was first revealed back in late 2005) may have surfaced over at the InsideMicrosoft blog (assuming they are legitimate):
Microsoft is currently developing Windows Mobile 7, the first revolutionary change to its mobile device operating system. Recently, I was given a document by a source inside Microsoft that details the touch and gesture plans for Mobile 7. This document is a confidential internal use only document, used to explain the plans for Mobile 7, and contains well over a hundred pages of designs, ideas, and changes to the way we interact with our mobile devices.
Windows Mobile 7 will bring new ways of interacting with the user interface. Not only will it support touch gestures (like the iPhone) but also motion gestures like shaking and twisting the device. The stylus will also play second fiddle to the fingertip although some devices will still require the latter (for example ones with screens too small).
Other improvements include new visuals along the lines of Vista, much improved Media Player and photo gallery applications and keyboard (although a full touch keyboard similar to that on the iPhone has been pushed back to a future version). Pocket Internet Explorer will support both tabbed browsing and desktop version of web pages. Windows Mobile looks like it will inherit the ribbon-based interface introduced in Office 2007.
And Microsoft is already planning Windows Mobile 8 which will support gestures in the auxiliary screen.
Windows Mobile appears set to ship in 2009. In the meantime, we expect to see the Windows Mobile 6.1 update.