It's called the 'burbs people and there are millions that live there. Chicago and Dallas are bother larger than Houston. Boston is about the same size as Houston when you take into white flight into consideration. My father grew up in a Chicago suburb because everyone around his family in the late 1960's left for the mega-ultra suburbs so they did like wise. Besides, I don't want Houston to get any bigger. I hate the traffic as it is, there're enough people from North Carolina to just barely tolerate and I miss all the open space, too much god damn concrete.
Using the 10 and 20 year growth rates, it'll be another 20 years or so before Houston surpasses Chicago.