Finally we have some concrete images of upcoming PR-3 or Symbian Belle uploaded at Nokia Forum. Its the new Qt UI which all the current and upcoming Symbian^3 devices will get.
The changes as you can see new the Signal and notification bar is now thin and takes very less space then current big n chunky one. This bar also work as Pull down to see all notification In menu the Back button has moved from right to left hand side, the icons are same as the upcoming PR-2 or Symbian Anna.
Take a look at new messaging app and calender app it has new Toolbar which has back button, dialer button, Refresh button (what to refresh in calender) and new options button. One more thing that I can notice is that there will be no persistent scroll bar in PR-3.0 or Belle like we have right now.http://www.youmobile.org/blogs/entry/Exclusive-Screenshots-of-Symbian-3-Belle-or-PR-3-0-UPDATE