Modulo the load on transportation and infrastructure--which seems likely to be substantial--to the degree that you're going to add that much housing, this seems a pretty sensible way to do it. It's generally impractical to bulldoze a large tract of low-rise housing to build slightly higher housing. So just about the only solution is to put high-rise housing somewhere that it has a minimal [EDIT: the least] impact.

That said, I wonder how well it will work to build a bunch of high-rise suburban housing while making it difficult for residents to have cars and without great transportation options.