"Almost there, Mayors," the tweet says.
SimCity's launch last year was plagued by widespread server woes that left the game--which required an online connection--completely unplayable for some. Maxis general manager Lucy Bradshaw said in March 2013 that an offline mode "didn't fit" with the company's vision for the game and later explained that introducing such a mode would require significant engineering work.
But in January 2014, Maxis finally revealed that an offline mode would indeed come to SimCity. When the mode goes live, all of your previously downloaded content will be available to you without an Internet connection.
For more on the engineering work Maxis needed to do to get an offline mode for SimCity ready, check out this technical breakdown by lead single-player system engineer Simon Fox.