Ocean Quigley, the creative director on SimCity, has left Maxis in order to start up a new studio, Jellygrade.
Quigley, along with fellow devs Andrew Willmott and Dan Moskowitz, confirmed his departure from the studio via Twitter, stating: "Yes - after SimCity 3k, SimCity 4, the Sims, the Sims2, Spore & the new SimCity, it was time for something new."
He then revealed a little about the new game that the studio are making. It's currently under the working title of Tethys ("but it'll probably change"), and concept art and a render can be seen here (and below).
"Still pretty early - the simulation engine is under active development," Quigely added, before revealing that the name for the studio came from the new engine being created by the fledgling team: "A bunch of the simulation is around fluid dynamics - it seemed right."