As far as I've seen from the last 2 years of living in this neighborhood, they're moving in and staying here. At least enough time out of the year that you don't notice if they're gone for prolonged periods of time (and it would be hard not to notice, the neighborhood is blanketed by solicitors and their ridiculous flyers). A few homes are known to be empty, but only a few, and this development has > 2k homes in it. There are a couple of rentals, but from what the neighbors and I have gathered there really are only a few. It's Irvine, CA, so it's just sort of like this, I gather.
edit/ Having said that, it's not very different from what you'd see in the San Gabriel valley in recent years, either. If they're living here full-time, or not, is any ones guess. I suppose I could find out if I really wanted to, but it'd probably take weeks.
Or are they investors who will stay in China?