There's really only 5 real classes of realignment I see as possible at this point (listed from most to least disturbing to status quo)

1. SEC and/or Big 10 expand with marquee teams, becoming even more dominant, and effectively break off from the other conferences with their own rules or prep to do so (either SEC alone or SEC and Big 10 depending on who expands where)
   
2. PAC12 poaches from Big 12 (wanting Texas/CST markets for next TV deal)
   
3. ACC adds Notre Dame and 1 or 3 other schools (they want it to be Penn St, but that's the same way the Big 12 dreams of Nebraska returning...not happening.  It would most likely have to be Cincy, WVU or UCF - though UCF is less likely with Miami and FSU already in conference)
   
4. Big 12 expands from G5 conferences (Boise, SMU, USF, Memphis, SDSU, UNLV, etc as options)
   
5. Rearranging deck chairs among G5s (so many possible permutations)
   

It's basically a given that option 5 will happen and not hugely substantive, but I think any of the other options are ultimately bad for the Big 12 and BYU (unless BYU is one of the teams that goes from Big 12 to PAC12 or ACC, in which case it's a more lateral move, but extremely unlikely)

There could also be follow-on actions from any of the listed setups