Hey!
As far as I am informed, EA has not done anything "big" with SimCity 2013 since its launching year.
After Maxis was shut down, a former developer there recently mentioned in an interview that SimCity 2013 without borders actually had been under discussion: "The eventual vision was that the whole region — the whole vast, 32-kilometer by 32-kilometer region — would be one potential city, and you could build anywhere in it" – Ocean Quigley, Former Maxis Director.
Even though, as far as I am concerned, EA has set them selves for some reason in "stealth mode" about SimCity 2013's future. Even though it had a disastrous launch caused by EA's ignorant and savage vision of a "online connected future" for its games, they did after all, after lots of pressure from the community, implement an Offline Mode. If issues with the servers was the main reason for the "Open World" to not succeed in reality, why not let us get to use it in offline mode? Mr. Quigley said indirectly in his interview that it was not that hard to bring it to life. With an offline mode, this would be a perfect and fair end of the story of a disastrous failure of a game.
Happy simming! (: