Eco Lifestyle Trailer features

I wonder how many lots there will be? Just those three or four in the trailer? I am wary with Del Sol Valley being so small that there may be a lot of shells placed beside liveable houses that we cannot access, especially as the town itself is dynamic. Or, do we build the new buildings rather than the game generate them as the smog gets cleared and the town cleaned? I feel as if the game does it itself and I have a feeling that will be used as a reason/excuse to not give us too many. We can already see that some don't change. I am guessing they are shells.