Nokia prepares new Symbian UI, the HTC Sense UI and the iPhone UI looking great. Although Symbian and Nokia are technically separate, they are, in fact, the same. The touch-based S60 5th Edition is supposed to look and feel better than the S60 3rd Edition, although improvements can still be made.
Scott Weiss, User Interface Technology Manager for The Symbian Foundation, is saying that S60 5th is just a temporary solution. Maybe in the near future another Symbian would improve the line, a S80, perhaps. The question that arises now is whether this is a new UI or is a fundamentally new platform altogether; an answer being hard to offer because these new devices will appear in 2011 or so.