- Mobile: mobile
- Enhanced XML support: xml streams (in 4.3 actually) and they are looking at a better xml tree implementation; XQuery/XPath are coming
- IPC: shared memory and locks, file mapping and local sockets ... all crossplatform
- Concurrency framework: multithreaded apps with mutexes and wait conditions in your app code
- Multimedia: audio and video playback. Yes, this is Phonon. =) QuickTime, DirectX and GStreamer backends are all coming.
- Help system: WebKit for rendering, componentized (viewer, index, contents, full text search)
- Fully resolution independent user interfaces (and then we can use this in Plasma instead of our own set of widgets)
- Qt for Cocoa: 64-bit Mac version based on the Cocoa API
- Next generation of Itemviews to make them rock a lot more, though just how was light on details; apparently this is an ongoing field of research right now for the Trolls
- More Qt Jambi, following the Qt release cycle
There are apparently plans for at least a 4.7 and there are no current plans for Qt5. If a Qt5 were to happen, it wouldn't be before 2011/2012 and it would not be a major API design break with Qt4 as Qt4 was to Qt3. However, they feel that Qt4 has what is needed for years of innovation to come and so there are no plans at all for a Qt5 right now.