[Yuri]

The US have added 33 million people/decade in 2000, in 2010 it slowed to 27 million and will probably be between 23-24 million in 2020. It probably go below 20 million on the next decade.

Those crazy scenarios for growth won't happen anywhere. Natural growth plunging, immigration on low levels, age average high and relatively much less people available on Rust Belt to fuel domestic migration to the Sun Belt.

About Houston, let's assume the add some sparsely populated counties (west and north) on their CSA reaching something like 35,000 km² of area (today it's 30,600 km² ). For a population of 15 million, that would be only 400 inh./km². That's less than England or Netherlands. At this point, as I said in one of the locked threads, it wouldn't work as a big metropolis, but a region with several nodes working as independent cities, with ultra-low density suburbs instead of fields between them. So even if those growth rates kept going, it wouldn't look like a metropolis like Los Angeles or London.