This time from a blogpost by @EAGamer himself: http://www.simcity.com/en_US/blog/article/state-of-simcity
Exploration for Offline Mode is Happening
Right now we have a team specifically focused on exploring the possibility of an offline mode. I can’t make any promises on when we will have more information, but we know this is something that many of our players have been asking for. While the server connectivity issues are behind us, we would like to give our players the ability to play even if they choose not to connect. An offline mode would have the additional benefit of providing room to the modding community to experiment without interfering or breaking the multiplayer experience.
City sizes have been a constant point of conversation among our players since we released the game. The game’s original design focused on the density of an intimate urban environment. It was about intercity connectivity and the challenge of managing a region of cities instead of one metropolis in isolation. However, we recognize that many players have expressed the desire to build up one big city rather than manage the interrelationship of multiple smaller cities.
We’ve put months of investigation into making larger city sizes, reworking the terrain maps, changing the routing algorithms of our agent-based system and altering the way that GlassBox processes the data in a larger space.
After months of testing, I confirm that we will not be providing bigger city sizes. The system performance challenges we encountered would mean that the vast majority of our players wouldn’t be able to load, much less play with bigger cities. We’ve tried a number of different approaches to bring performance into an acceptable range, but we just couldn’t achieve it within the confines of the engine. We’ve chosen to cease work on bigger city sizes and put that effort into continuing to evolve the core game and explore an offline mode. Some of the experiments we conducted to improve performance on bigger cities will be rolled into future updates to improve overall game performance.