ARM and Microsoft signed a licensing agreement for ARM architecture. "The agreement extends collaborative relationship between two companies. Since 1997 Microsoft and ARM have worked together on software and devices across embedded, consumer and mobile spaces, enabling many companies to deliver user experiences on a broad portfolio of ARM-based products."
wARM chips are widely used in mobile device market which could indicate that Microsoft has plans to release their own branded mobile hardware with dedicated ARM chip, something along lines of future Zune device (it currently uses a Tegra chip from Nvidia). Microsoft might also work on a chip that it'll offer to OEMs to really get most of its software. This licensing agreement could be used to get more out of Windows Embedded or Windows Phone or even a future version of Windows, such as 8 or even further into the future. Microsoft could also be aiming to overhaul its Xbox architecture with a new ARM chip.