There's been a section of I-10 West of San Antonio that has had a posted speed limit of 80 for years (I think about five years). It was actually pretty nice crusing that long stretch at about 5 over.
I don't see a problem with the new speed. Most everyone drives 5-7 over anyway. Texas is unique in most of its Interstate Highways. Where else can you drive in one direction for 10-12 hours and never leave the state?