Microsoft's next generation of Office, codenamed Office 15, will receive interface tweaks to make it more touch friendly on Windows 8, including a radial menu system, but won't be rebuilt as full "Metro style" apps using the new WinRT programming model. That's the word according to our sources, who say that the core Office applications will be flatter, feature more white space, and use fewer lines in an effort to focus on content, but that the look will literally be window dressing — Office 15 apps will still be traditional Windows apps underneath. We can't immediately verify all of the claims, but in addition we're hearing that the ARM version will also be desktop applications, running in a restricted Windows 8 ARM desktop mode designed for power efficiency.

Microsoft's choice for Office desktop apps in Windows 8 appears to be a matter of time constraints. One source indicated that plans to build a true Metro style Windows 8 version of Office have been pushed back as the Office team would have to overhaul the entire suite to take advantage of WinRT, adding time to the software development process. Microsoft's design lead, Steve Kaneko, is upbeat about the improvements, saying people will be "really impressed" with Office 15.

Microsoft is, however, building at least two Metro style Windows 8 Office applications using WinRT. OneNote and Lync will both be released as Metro style applications, presumably in the new Windows Store. The apps are less complex than their Word and Excel equivalents, perhaps easing their ports to Windows 8 Metro style and iOS — they're already on the iPad, presumably to hook users onto associated Microsoft services like SkyDrive and Office 365. Microsoft announced its Office 15 Technical Preview this week, with a beta due in summer, and we expect to hear a lot more about the future of Office in the coming months.