Yes, currently this would be the tallest building in Austin by 65 feet, beating the Frost Bank Tower. But there are two 700 footers proposed as well. One is supposed to be "atleast" 705 feet with 47 floors but will likely be taller than that. And the other will be "atleast" 700 feet with 48 floors. Both developers of these two buildings say their buildings will be the tallest in the city.
Exciting times in Austin.
You can read about both new 700 footers in this thread. There's renderings and articles on both here:
http://forum.skyscraperpage.com/showthread.php?t=105174