Maxis has stated that there are server calculations needed to simulate SimCity
and that's why the need for a persistent connection. Well. does it?
A few folks have played the game well beyond their disconnection status and an anonymous developer has talked with Rock Paper Shotgun
that the servers aren't doing any calculations at all in your city. They also stated that a lot of what the server is doing is checking to make sure the person isn't cheating and that it wouldn't take much effort to do a single player option without all the region features.
Now, developers can be a quirky lot. Some know what they are talking about, some don't. Depending on how much they've worked on the project, some can tell what can or cannot be removed so it doesn't break something. As a developer myself on medium and large projects that I have worked a lot on, I do know a lot of what can be removed before things start to break down. On some projects where I worked a small amount of code on, no, I cannot. So for this person to know if removing the server requirement wouldn't break the game, that's hard to say if they really do without knowing how extensive they worked on the game.
I know some folks said Maxis tried something different. I don't fault them for that. The implementation was the problem and, of course, available resources for those that wanted to play the game. And, I think the audience for SimCity are many who just want to build and destroy their own cities. The game's called SimCity, not SimWorkTogetherInRegionsOfSmallCities. A great deal of folks, I think, just want to play on their own at their leisure and just have fun. There's still a mass market for single player games, and SimCity is one franchise that his that market.
In the end, I hope they get it all worked out well so people can have fun with it and talk about the game itself, rather than the problems.