Windows 9. To distance itself from the Windows 8 debacle, Microsoft is currently planning to drop the Windows 8 name and brand this next release as Windows 9. That could change, but that's the current thinking.
BUILD vision announcement. In case it's not obvious that the Sinofsky era is over, Microsoft will use BUILD to provide its first major "vision" announcement for Windows since, yes, Longhorn in 2003. Don't expect anything that grandiose, but the Windows team believes it needs to hit a happy middle ground between the KGB-style secrecy of the Sinofsky camp and the freewheeling "we can do it all" days that preceded that. As important, the firm understands that customers need something to be excited about.
No bits at BUILD. Microsoft will not be providing developers with an early alpha release of "Threshold" at BUILD, and for a good reason: The product won't even begin development until later that month. Right now, Microsoft is firming up which features it intends to deliver in this release.
Metro 2.0. Maturing and fixing the "Metro" design language used by Windows will be a major focus area of Threshold. It's not clear what changes are coming, but it's safe to assume that a windowed mode that works on the desktop is part of that.
Three milestones. Microsoft expects to deliver three milestone releases of "Threshold" before its final release. It's unclear what these releases will be called (Beta, Release Candidate, etc.) or which if any will be provided to the public.
April 2015 release. Microsoft is currently targeting April 2015 for the release of Windows 9 "Threshold."