According to CVG, The Simcity series is set to make its return and will be officially be announced via the next Official Games for Windows Magazine. The fifth installment is allegedly called "Sim City Societies" which may mean more focus on the actual individuals that inhabit the city. I am a longtime player of the Simcity series and one improvement that i would like to see is the better performance of the game engine.

More info as it becomes available.