heres some info about symbian^4 from symbian foundation blog

Symbian^4

Planning for Symbian^4 is at an earlier stage. It follows Symbian^3 by around six months.

The following technology contributions are expected to be fully integrated for Symbian^4:

* Qt optimised for the Symbian platform – Qt is a well-liked application and UI framework;
* A new “Orbit” extension library for Qt, which contains more than 50 widgets tailored for mobile user experience, and which will provide a replacement for the existing “Avkon” widget set;
* A new “Direct UI” interaction and navigation logic, combined with finger-optimised layouts offering excellent touch and hybrid-device user experience;
* The application suite re-factored and re-written to take advantage of Qt APIs, Orbit widgets, and Direct UI.

Elements of this combined offering will of course be available for experimentation ahead of their full integration in Symbian^4.

http://blog.symbian.org/2009/04/30/r...-release-plan/