Assuming this happens, what does it mean for the other conferences?
The only thing that a Texas A&M move to the SEC assures is that the Big 12 is dead. There was some possibility that if Oklahoma could convince Texas to stay in the conference the Big 12 could continue on, less Colorado and Nebraska, and still function. The conference would be weakened, but not fatally so.
With the move of Texas A&M, however, the conference will only have nine teams. While a nine team conference with Oklahoma and Texas could still survive, it's doubtful that Texas would want to stay in such a weakened group, when it has better prospects elsewhere. The only thing holding Texas back from leaving the Big 12 until now, was, presumably a desire to avoid the accusation that they had killed the conference, as they did in the past when Texas led a group of four schools from the Southwest Conference to the then Big Eight. If Texas A&M becomes the third school to bolt the Big 12 in the last week, then Texas has the cover it needs to leave as well.
Given that the Big 12 is almost certainly dead, three possible scenarios seem possible, from most to least likely:
1. Texas, Oklahoma, Oklahoma State, Texas Tech, and Utah head to the Pac-10.
This is the option that seems likeliest at the moment, what with reports today saying that representatives of the Pac-10 met today in Oklahoma City to issue formal invitations to the two Oklahoma schools of the group.
If this happens, the Big Ten would likely turn its attention to Notre Dame, some combination of Rutgers / Syracuse / Pitt, or Maryland, which has surfaced as a dark horse candidate in recent weeks because of its connection to the Washington, D.C. area media market. Mizzou is also a possibility, albeit unlikely at this point.
This move would also likely prompt the MWC to push hard for the acquisition of the Jayhawks, who, with the demise of the Big 12 would need a new home. If the Big Ten was not interested in Missouri, they could also be an addition.
As far as the SEC is concerned, the acquisition of Texas A&M would push that conference to 13 schools, and if they wanted to preserve their annual championship game (which they almost certainly would) they would need to add another. There have been reports that they were targeting ACC member Virginia Tech, however, it seems unlikely that VA Tech would want to abandon its rivalry with the University of Virginia. Were the conference unsuccessful in regards to VA Tech, they could also attempt to poach Florida State or Georgia Tech.
Another possibility is the University of Memphis. A report out today says that FedEx is willing to commit ten million or more dollars annually to any BCS affiliated conference that takes the University of Memphis in. While the SEC could be a possible candidate to balance out the acquisition of Texas A&M (both numerically and financially), the most likely candidate would be, according to the article, the Big East -- if, that is, the Big Ten poaches a few of the members of that conference. That conference is certainly more cash starved than the SEC is, and, if the Big Ten did take some of its members would also need to replenish its ranks as soon as possible.
Note: An astute reader pointed out that I originally had six schools listed as moving to the Pac-10, with the addition of Colorado to that conference last week, it would only need five to form the Pac-16. Of the candidates listed, Baylor then would seem to be the most likely to get chopped, or Utah/Kansas. This could change if Oklahoma joins Texas A&M in the SEC and Texas still doesn't decide to move to the Big Ten.
2. Texas, Texas Tech, Oklahoma, Oklahoma State, and Kansas move to the Pac-10.
This scenario is less likely, as Utah has seemed the favorite in recent days.
If it happens, though, expect Utah to stay put in the MWC, with that conference looking hard at the remaining Big 12 schools, Missouri, Iowa State, and Kansas State. C-USA and the Sun Belt are also possible homes for those schools.
The outcome for the Big Ten and SEC would likely be the same as in Scenario One.
3. Texas moves to the Big Ten (aka all hell breaks loose)
The least likely of all the possibilities at this point, this scenario is still on the table until the press conference announcing the move of the Big 12 south teams to the Pac-10 actually occurs. Texas A&M moving to the SEC would give Texas a bit of political cover if it decided it wanted to head to the Big Ten for financial and academic reasons over the Pac-10. What would really push this scenario further into the realm of possibility, though, is Oklahoma making a last minute jump from the Pac-10 to the SEC alongside Texas A&M. OU seemed to prefer the cash opportunities in the SEC to that in the Pac-10, but wanted to preserve its rivalry with the Texas schools. If they could be convinced to join Texas A&M, however, things would get crazy rather quickly. With two of the Big 12 south schools leaving for the SEC, the Longhorns would really have cover to move to a conference not including Texas Tech or Baylor. That conference could be the Big Ten.
If the Big Ten were to somehow add Texas, it would likely not stop at 13 teams. At that point, Notre Dame becomes the likeliest candidate to round out the conference to 14, with the Big East schools and Maryland / MIzzou lagging behind.
As far as the rest of the Big 12 was concerned.... it's possible that some combination of Texas Tech, Baylor, Oklahoma State, and Kansas would look to the Pac-10 still. Though, the Pac-10's revenue is low as it is, and without the heavyweight that is the University of Texas, it seems to me that it would be difficult to convince Pac-10 member schools Stanford and Berkeley to accept the somewhat academically challenged Texas Tech and Kansas. Since a unanimous vote is required in the Pac-10 to admit new members (unlike in the Big Ten, which only requires 8) the loss of Texas from the deal could derail expansion for that conference permanently.
At that point, the most likely homes for the Big 12 teams would again be the MWC, C-USA, or Sun Belt. However, that group of Big 12 south teams may not be able to move as a unit, especially if they look to the MWC. Word on the street (ESPN Insider) is that TCU has no interest in Baylor joining their conference, and would move to block such an addition to the MWC, as payback for TCU's exclusion of the formation of the Big 12 when the Southwest Conference fell apart in the mid-90's.
In any case, Texas to the Big Ten and Oklahoma to the SEC with A&M would cause the type of instability that virtually guaranteed re-alignment moves to continue throughout the summer.