If you've tried the SimCity betas and thought the cities too small, well, that could change in the future.
As it stands, Maxis is putting a bit of a limit on the game for performance issues, so more people can actually play it. Creative director Ocean Quigley has stated, however, that there is an interest in expanding over time.
On this note, Quigley explained:
“That is just a performance decision. Given that was the performance constraint we decided to work under, we built a larger region environment and a bunch of the multiplay to work with 2km cities. At some point in the future, especially with mainstream computers become more capable, we could certainly make the city sizes larger.
"We need to keep in mind that Sim City is a mainstream game, it’s not a game that is only going to run on high-end gaming PCs, it has to run in your Dad’s PC as well.”
Bear in mind this isn't a guarantee, which Quigley wanted to specify as well, in case anyone got the wrote idea. While Maxis is certainly interested in expanding the sizes of SimCity's cities, they can't make any promises right now. It's really more a question of "if" than "when," right now.
SimCity will be out on March 5 for PC.