According to an article on tamss60, Symbian S60 is just about dead and is to be phased out over the next few years to make way for a new development stack according to David Wood.
Expected to solidify around the second half of 2010, UI toolkit Qt will replace S60’s Avkon API around Symbian 4, which means current Symbian S60 apps will break except for low level stuff not using Avkon UI elements.
It’s a big thing considering the installed base of Symbian S60 applications and users, but obviously needs to be done and done quickly like ripping a plaster off a hairy arm.