Yep. Simcity 2013 runs the entire simulation on one core no matter how many cores your PC has. This, the small city sizes, and the always online DRM, are the three reasons why I didn't buy the game. It's utterly ridiculous for a data intensive game in the year 2013 to only run on one core exclusively. Totally shortsighted and stupid design decision on the part of Maxis.
My gaming dollars are my votes for the games I like, respect, and support. I just wouldn't be able to respect myself if I had bought the new Simcity game with the way they designed it, even though I own every other Simcity game, I love the franchise, and I still play Simcity 4 to this very day, but come on. Now, in retrospect with how the launch has gone, I'm damn happy I listened to my gut feeling. I never thought it would be THIS bad a launch, I mean Holy Hell.
If they ever add an offline mode and support for larger cities (which I'm sure would only happen if they go multi-core) then I'll happily buy their game. I WANT to buy that game, Hell I'd gladly pay $100 for it. Hopefully they release it someday...