Grant Rodiek has published a new blog with information on the upcoming Expansion.
The main information is that your Architect Sim will be able to enter a special "in-game mode" to redesign houses in the neighbourhood. Sounds easy, but your Sim has to have an eye on the budgets as well as certain customer wishes.
The Stylist and Tattoo Artist have a similar feature where they'll be able to change the hair and make-up or tattoo a Sims.