Here's a look at a number of buildings u/c or proposed that are over 500' in Dallas, Austin and Houston. May have missed a few but I've only included projects that plan to start this year or 2019.
Dallas
AMLI Fountain Place: 562' | 45 floors, u/c
Austin
6 X Guadalupe: 848' | 65 floors, late 2018/early 2019 start
The Independent: 690' | 58 floors, late 2018 completion
mopacs
The Travis: 595' | 55 floors, early 2019 start
Block 185: 592' | 35 floors, 2019 start (tenant reportedly secured)
*
rendering n/a
Block 71: 542' | 36 floors, site prep
Houston
Block 58: 735' | 47 floors, site prep
3200 Post Oak: 51 floors, 2019 start
The District: 631 & 544' | Mid 2019 start
Capitol Tower: 579' | 35 floors, 2019 completion
Houston Sunset by
brijonmang, on Flickr
Block 42: 545' | 46 floors, construction start imminent
The Allen: 42 floors, 2018/2019 start