The Symbian Foundation share details of symbian 3 at mobile World conference. Some of the features explained were:
1.HDMI support : It will support hdmi 1.3a and above plus hdcp. Just connect to tv and watch the videos.
2.Full remote control for your music player: It can peruse any media player that supports Bluetooth AVRCP v1.4.
3.Music store integration : Much like Phone 7 they too have integrated it.
4.Podcast management:Subscribe to news.
5.Improved 2D and 3D graphics: For better gaming support.
6.Improved and optimized UI:It will now have single tap interaction , multi touch gesture and faster ui due to better architecture.
7. Better data networking : It will supports 4G.

It is based on qt4.6 ( same qt thing on which kde is based).
Symbian is the current leader in world with 45% share and it must be noted apart from android and some other Linux mobile remains only one with multitasking support. It is also open source now onwards.