Here's how Microsoft describes the conference:
At Build, we’ll share updates and talk about what’s next for Windows, Windows Server, Windows Azure, Visual Studio and more. Build is the path to creating and implementing your great ideas, and then differentiating them in the market. Pay a visit to www.buildwindows.com, get yourself registered on April 2, and join us for three days of immersive presentations delivered by the engineers behind our products and services, while networking with thousands of other developers getting the first look at what’s next.
The bulk of the content is likely to focus on desktop technologies, with the smart money on an officialy unveiling of Windows "Blue", but developers may also receive some hints on future technology for the Windows Phone platform. Moreover, Microsoft sees the Windows Phone platform as an integral part of its multi-screen experience and wider Windows strategy, something that's underlined in the announcement blog post:
In the past year, we’ve introduced an assortment of new opportunities to build incredible apps and experiences on Windows, and developers all over the world have taken advantage of it. Just look at the last few weeks - we’ve seen great apps like Twitter on Windows 8 and Pandora on Windows Phone 8 as great examples of developers really taking advantage of the platform in a way that users love. But we're also seeing users increasingly expect their experiences on multiple screens, and Skulls of the Shogun is a great example of how Windows is the best place for developers to capitalize on the opportunity.