Aggie here... hope to add some perspective, but in reading the board, it seems in general we share the same reservations already.
I haven't talked to an Aggie yet that is happy about this. Most I've circled up with had similar initial reactions as me. First gut reaction is "Hell no". Then when the reality sets in that conference realignment has been anticipated for a while and seemingly inevitable, it makes some sense.
So on some level, the idea it may be entertaining to re-kindle the rivalry rambles around in our brain. But Longhorns ("tea sips" to us) will tell you we ended the rivalry and didn't want to play them after we left the Big 12. Complete the opposite if you follow the public press statements of the schools - we stated we would be open to finding a way to keep it going, they backed off. We're happy just not playing it, now. And this is even my opinion, a '93 Texas A&M graduate, former member of the Corps of Cadets and a romantic at heart. I have ticket stubs my grandmother kept from the Texas A&M vs Texas rivalry game in 1929 (Aggies won), and cried at the 1999 Bonfire Game; I still think fondly when the Longhorn Band dipped their flags and raised A&M flags at the end of their routine, after playing Amazing Grace. That was the only moment ever I have to commend them.
Then the arrogant antics all the other years and lack of straight dealing in conference matters comes back to mind.
As you may be aware, our relationship with them deteriorated slowly over decades. There was a time Texas A&M simply couldn't compete with them. We were an all-male military college until 1965. We were fully co-ed by 1975. We had some lore, like Bear and the Junction Boys, but thinking we could compete with them prior to that is like saying West Point or Annapolis should be able to compete with Michigan or Ohio State. In the years from 1975 to the end of the rivalry in 2011, our record head to head was even. Yet they lived in the past when it came to dealing with us on conference matters.
Texas killed the SWC. To be fair, the SWC was dying as modern football advanced and the value of media contracts became more known. Arkansas left it for the SEC, no doubt partly because of how Texas tried to run the conference. But, to be fair, the SWC was doomed as it was (after Arkansas's departure) --- a Texas-only conference with schools like SMU, Rice, UH, and TCU. Texas A&M dominated it in its final years, with a 14 - 6 record vs Texas in the final 20 years, and 10-1 in the final 11 years (with the 1 being a 1 point upset against us in Austin). This was unbearable for Texas. Rather than working in the conference, or with Texas A&M for that matter, they instigated a move to the PAC 10 in the early 1990s and simply assumed they would "carry us there." Texas A&M had actually already been interested in joining the SEC since the late 1980s. While there were structural problems to the SWC that weren't UT's fault, their arrogance in dealing with conference mates was showing, nor had they recognized "little brother" grew up decades prior. Their attitude then was the death nail. Texas A&M would have been happy joining the SEC in 1995, but political powers in the state kept A&M and UT together in forming the Big 12.
Most are in tune with the more recent history of the Big 12. Of course, the Aggies and Missouri left it to join the SEC in 2012 (and I couldn't be happier about it almost a decade after). But let's not forget a couple years before we left, Nebraska and Colorado also left, no doubt they had had enough of UT, its propensity to want to run a conference, dealings merely for itself without working inside the culture of the conference (e.g. Longhorn Network), etc. The "original Big 12" was victim #2 in their conference killing career.
Now we sit here today. We knew the "current Big 12" was on life support. Victim #3. Texas still hasn't recognized the world around them is not the same as it was decades ago. Texas A&M's reasons for joining the SEC have all come true: a) better cultural fit, b) desire to be fair dealing in conference matters, c) more money (Forbes most valuable program in recent articles), and d) recruiting.
Bringing me to full circle... I don't yet trust that the Longhorns have changed.
I don't believe they are a cultural fit. It is well-documented they would rather go west to the Pac 12 "because they are more aligned with our academic standards". Texas and Texas A&M are vastly different culturally (liberal school vs conservative, respectively).
I don't believe they have changed their views on dealing in conference matters. I hope the SEC can prove me wrong and will actually keep them in check. I hope they forfeit their LHN contract buyout to the SEC. I hope the SEC does allow the "horns down" so long as it's not done like any other gesture that can reasonably determined to be taunting. Please SEC, prove me wrong.
On the point about more money, they are obviously motivated by it, as of course we all are. I personally don't care if they make more in the SEC than other options, so long as the SEC's formula of equality on this matter isn't compromised. Three conferences have died proving the SEC's model works.
As for recruiting, I don't buy our own AD's and many of our fans' narrative that it hurts our recruiting. Jimbo has been recruiting nationally, and the SEC has been recruiting away from Texas for years, more so since the Aggies joined the league. Not sure how UT joining really shakes that apple cart. Our recruiting improved when we joined the SEC mainly because we were out of the Big 12 and it was appealing to a recruit they would play in the SEC, which had nothing specifically to do with UT. Of course, it's easier on us to keep them locked out, but not necessarily a battle we can't win against them.
Anyway, what seems "inevitable conference realignments" aside, not a fan of UT and OU joining. Hope I'm wrong.