This announcement was supposed to take place next week, but news of it was just announced early from UDS Budapest. Qt 4 was the last major release of this tool-kit more than six years ago, but Qt 5 will come in the 2012 calendar year with several key improvements.
Qt 5 will be modularized, target Windows / Linux / Mac OS X as primary support targets, and deliver on Qt Quick 2.0. Qt Quick 2.0 will leverage OpenGL scene graph and support text scaling, shader effects, faster texture uploads, and v-sync driven animations. Using OpenGL scene graph should be a huge win alone and will be v-sync driven.
Prior to Qt 5, the Qt 4.8 release will be here in just a few months. "In the next couple of months," it will be released. The Qt 4.8 release will focus on bug fixes and improving the performance. The file-system back-end has also been completely rewritten. There's also the new Lighthouse architecture. Using Lighthouse makes porting Qt new platforms -- like Android and iOS -- much easier.
Qt 4.8 will be more Wayland friendly with the Qt Compositor, but the real Wayland love should be here with Qt 5.
Nokia has also just announced that they will be moving Qt towards a matter of open governance for the open-source project. This will affect their work-flow, method of accepting patches, road-map development, release management, quality assurance, tooling, communication, etc.