The whole thing between A&M and Texas is so petty on both sides right now.
Texas swears they're not rivals, they don't care about A&M, A&M can't exist without Texas and Texas will refuse to play A&M if they leave for the SEC...
A&M fans are tired of the BS and want to competely cut ties with Texas. Don't care about playing them in the future because it would weaken Texas' schedule and there's no need for them to add Texas to an SEC slate.
Both sides jabbing at the others fight songs when BOTH of their songs have lines about the other...
They both need each other. Different conferences or not, they're both better for playing the other across every sport. They generate big chunks of money by playing each other and neither school is going to want to give that up.