Hmm, I did not consider that. I guess we'll see in a decade or two. My opinion is that many of these constructions will go unused - permanent relocation is a lot harder than just using roads, plus no doubt most of them have already been bought for resale (increasing the price) or rent (which may be more acceptable). Also, there are whole apartment blocks in or near major cities that are still unused despite demand, it's not just ghost cities.