RuneScape 3 won't require players to create a new account. Players will simply keep using the same avatars they always have. The game will take advantage of the HTML5 engine and web GL to run faster, look better, and suck players in even more deeply, though folks running with older computers will still be able to use the old Java client if they prefer. Jagex is promising more details in the coming weeks.
Skip below the cut to check out the announcement video.