A lot of potential lots that could of been added is lost honestly.
It isn't just the new worlds, but some previous worlds like San Myshuno, there was the potential for at least 5 more apartment buildings to be used with two in the spice market (both either side of the Culpepper apartment) and two more in the arts quarter (one in front of Medina Studios and the in front of FountainView) as well and the final in the fashion district just below the penthouse using the other doors as entry and exit point.
Sulani had some fake houses as well that could of been used to effect in Ohan'ali Town and Lani St. Taz.
Willow Creek is littered with fake houses that could of been used, an expansion on Foundry Cove for example could of yielded a second street with lots on the same side of the road behind Garden Essence and Daisy Hovel. Same could be stated for the Crawdad Quarter across the busy street, there are a line of fake houses there as well. I also recall one other fake house in the Sage estate the other side of a small road near the shoreline.
Oasis Springs is also filled with fake houses, there are two up on Acquisition Butte, one on the right side of Yuma Heights and the other behind it. Parched Prospect could be expanded out to include houses behind Raffia Quinta, Dusty Turf and Cacti Casa, but there are a few fake houses on the right side of Cacti Casa past the bend in the road. The same could be stated of Bedrock Strait if the world was expanded out to include those as well.
There is plenty of opportunity in Strangerville as well, lots of lots about that could of been used in town but we only get access to just three plus the local bar and library.