The April timing for the developer conference would put it after the anticipated completion date of Microsoft's proposed acquisition of Nokia Devices & Services business. One of the key topic for the conference is expected to a full introduction to the developer details of Windows Phone 8.1, the next major release of Microsoft's mobile platform. Other topics are likely to include spring updates for Windows 8.1 and the Xbox One, together with details on the latest revisions of Microsoft's wide ranging enterprise, productivity, and server software.
Microsoft has not yet publicly commented on Windows Phone 8.1, though an initial announcement is widely expected for the first quarter of year, with some rumours suggesting the first devices will be announced at the annual MWC conference in Barcelona (24th - 27th February).
Update:
Microsoft has now officially announced the dates for BUILD 2014 on the official Microsoft blog:
It seems like we were just gathered in San Francisco for Build 2013 and yet a lot has happened since that time. Windows 8.1 is in the hands of consumers and there is a great selection of new devices at all sizes and price points coming in time for the holidays. Last month, we released Xbox One and sold more than two million units in the first 18 days. And we continue to see the addition of great new apps, with differentiated user experiences, coming to the platform from top names such as Flipboard, Instagram, Waze, Vine and Mint alongside thousands of local apps growing every day.
The momentum just keeps building and that is why I’m so excited to announce our next developer conference, Build 2014, which will take place April 2 to April 4 at the Moscone Center in San Francisco. Save the date and mark your calendar for registration, which opens at 9 a.m. PT on Jan. 14 at www.buildwindows.com.