As reported by the Statesman today, the Census Bureau estimates that Austin has vaulted into 11th spot on the list of largest American cities.
This is a good time to remind people that measuring city populations using legal city boundaries is, for most purposes, meaningless. Which side of a particular boundary you live on certainly might affect your taxes or the quality of your city services. But when talking about the features of a city that depend somewhat on its size -- the traffic congestion, the variety of restaurants or movie theaters or bookstores -- you have to count the central city plus the suburbs, because people cross city boundaries to work, to shop, to eat, to go to the movie and even to attend school. For these purposes, it's better to use the city's urbanized area, which is, roughly, the central city plus contiguous areas that exceed a certain minimum threshold density. (The precise criteria are more complicated.) Loosely speaking, the city's "urbanized area" is what you would circle as "the city" if you were looking at a nighttime satellite image of the area.
Austin's urban area population grew dramatically between 2000 and 2010, but as you can see, we're still just No. 36:
Note that Austin's 2010 urban area has slightly more people than San Antonio's 2000 urban area. The same was true with metropolitan area populations. Austin is almost exactly 10 years behind San Antonio in growth.
(Also note the effect of Katrina: In 2000, New Orleans' urban area had 10% more people than Austin's; today, Austin's is 50% larger.)