Datacenters seem very unlikely. In the past, Google has shown a very strong bias toward building datacenters in areas with very cheap hydro or tidal power. Solar is a possibility here, but building a datacenter with enough solar panels to power it and enough batteries to keep that power uninterrupted at night and on cloudy days seems unlikely. (It would explain the size of the site and proximity to the Gigafactory, though.)<p>I would bet on some sort of test location for various Google X moonshots - self-driving cars, Loon, Wing, and probably others. One challenge Google has with its Mountain View location is that everything that goes on there gets reported in the press; it's very difficult to keep new projects secret there. The race to self-driving cars (& subsequent industrial espionage) is proof of that. A giant test site in the Nevada desert would make it much easier to hide new products. It'd also explain the size & proximity to the Gigafactory; I'd bet that several of these new product ideas require batteries in some form or another.