The city, whatever one they go with, is only a part to what makes this series so entertaining. In III LC was supposed to be a facsimile of NY. It didn't look anything like NY outside of the three island or landmass concept. What made III so good was the story, gameplay, soundtrack and visuals (for the time) all blended to gether so well. The same can be argued for the rest of the trilogy titles.
I'm sure the city visually will be amazing. It is what is in and can be done in the city that will make the game great and replayable.