The Texas Longhorns and Texas A&M Aggies will play on Thanksgiving Day in football, and then on various other days in various other sports that probably have schedules freely available on the Internet and accessible via Google. After that, they won't play each other in football again until 2018 at the earliest due to Texas' plans to stick to its current non-conference schedule.
A&M will leave the Big 12 for the SEC in 2012, in case you're just now joining us.
To be sure, non-conference schedules can be broken. For example, this year's Chick-fil-A game between the Boise St. Broncos and Georgia Bulldogs required both teams, plus the Louisville Cardinals and North Carolina Tar Heels, to rearrange their schedules, and all on short notice to boot. Texas could very easily buy out a couple of non-conference games years down the road to make room for their longtime rivals.
Thus, this is a pretty clear shot at the Aggies, and not anything Texas was forced into doing. Not that I'm judging Texas for having the last word here.