I understand realignment is driven by money, but somewhere a bigger pie won't make up for more slices in terms of the number of members and the available weeks for the members to play each other. Currently there are 12 weeks to a regular season. All teams will want to play non conference opponents to maintain non-conference rivalries, get in trial games, and gain exposures. Thus I believe most teams will want at least 3 non-conference games and this will leave 9 for conference plays. A ten teams conference such as the Big XII has a nine games conference schedule. However, a ten teams conference cannot hold a conference championship and loses out on an extra game to make money for the conference. If the championship game can bring in the cost of having two additional teams over ten then this will be a win win for the conference. A twelve teams conference with two divisions of 6 would yield 5 in-division games and up to 4 cross-division games. A fourteen teams conference with two divisions of 7 would yield 6 in-division games and up to 3 cross-division games. A sixteen teams conference with two divisions of 8 would yield 7 in-division games and 2 cross-division games. However, 2 cross-division games against 8 teams mean one home and one away staggered results in 2 games every 8 years; might as well not be in the same conference. Thus I believe 16 teams conference is unwieldy. Thus I see 12 or 14 as the ideal size for a conference.
Thus when looking at conference expansion and realignment, I believe most major conference realignment must consider their current size as well as well as expansion options. By major conference I mean the big 5 as classified by the BCS starting 2014 to be the B1G, SEC, Pac12, BigXII, and ACC.
The B1G just acquired Rutgers and U Maryland to go to 14. I do not see them expanding further anytime soon and I do believe when they go looking they will want an AAU school. Westward there is only Iowa State but the B1G is already in Iowa and there just isn't much to gain by adding Iowa State. Kansas is unlikely as they will not travel without Kansas State. Southward there is the SEC and they are happy where they are. Eastward are UVA, UNC, Duke, and Georgia Tech. These are all ACC schools and I will express why none of these schools will leave for the B1G.
SEC is already at 14 with the recent addition of Texas A&M and Missouri. The only candidates they would look for would be a North Carolina school and a Virginia school to expand their footprint. Again these are ACC programs and I do not see them leaving.
Pac12 is currently at 12 but their expansion options are limited now that the Texas and Oklahoma schools have locked themselves in with the Big XII. There are six potential candidates for the Pac12 and they are BYU, Hawaii, Nevada, UNLV, Colorado State and Utah State. Given the current structures of the Pac12 membership of 2+ schools per state, the U and its sibling State U, I can see the next two additions being Colorado State and Utah State. I just do not see BYU or any other MWC teams being invited.
Big XII is currently at 10 and will expand. They can take 2-4 teams given that they already own the rights to the Big XIV. Who they take will depend on what happens with Maryland exit from the ACC and the $50 millions fee. If Maryland's exit goes well and not have to pay most of the $50 millions, then the Big XII will raid the ACC for Florida State and Clemson or Miami to go to 12. If Maryland's exit is difficult, then it will be difficult for the Big XII to buy out an ACC team in the same manner the B1G can help with Maryland's exit. In that case I believe the best candidates for the Big XII are Louisville, Pittsburgh, Cincinnati, South Florida, Northern Illinois, and BYU. Though committed to the ACC, that they are not yet full members and thus, like TCU, may be able to leave with minimal cost. Pittsburgh would make a great regional partner for West Virginia and resume the backyard brawl rivalry. Pittsburgh is also a good market, a good program, and reasonably competitive in football. Cincinnati could be taken with Louisville for the regional synergy with each other as well as with Pittsburgh and West Virginia. Again the Keg of Nail rivalry between Louisville and Cincinnati would be preserved. Three teams would result in an odd number and team number 14 will be needed. South Florida will bring the Big XIV to Florida but will be on its own without realistic prospect for a future partner other than Miami. BYU would give the Big XIV an national marque. Northern Illinois will be considered only if they win against Florida State in the Orange Bowl as they might make a nice regional rival for Iowa State and provide a foothold in the Chicago market.
The ACC conference will hold largely because the core of the conference are the North Carolina schools and the Virginia schools, much like the Big XII held because of Texas and Oklahoma. These 6 schools, UNC, NC State, Duke, Wake Forest, UVA and VT will allow the ACC to endure, and as such so will BC. Whether Clemson, GT, FSU and Miami leave will depend in part on what happens with Maryland's exit. GT is attractive to the B1G and will need a partner to be taken, but Clemson, FSU and Miami are not AAU members. All four might be attractive to the Big XII. If the Maryland exit is difficult these four teams will not leave. If the Big XII then take Pittsburgh and Louisville, the ACC will counter by taking UConn (despite BC resistance in order to maintain a northern foothold with Syracuse), Navy and South Florida (possibly). My bet is Clemson, GT, FSU and Miami will all stay with the ACC.
In my opinion the Big East, without the Catholic BB schools, and without Boise State and probably SDSU in football, will likely cease to exist as an independent FBS conference. Some have suggested some sort of merger with CUSA and I think this is reasonable. The alternative is to build itself as a new football conference but with membership consisting of Temple, Navy, UConn, Cincinnati, USF, UCF, ECU, Memphis, Tulane, SMU and Houston, this grouping of teams has neither cohesion nor identity to exist as a whole.
Of the minor conferences, I believe the MAC appears most stable. With the addition of UMass they are at 13. They should be searching for a 14th and the best options are Temple (which was a member before bolting for the Big East), UConn (if they are not taken by the ACC), Marshal and Western Kentucky (both current CUSA members), and possibly Army.
The MWC will got to 12 with at least Boise State and SDSU. They could go with 14 with SMU and Houston, both Big East invitees. SMU and Houston will move west only if they believe the competition is better in the MWC, to recruit in California rather than Florida, and thus potentially lay the exposure groundwork in Pac 12 markets for future considerations by the Big XII. Neither are candidates for the Big XII or the SEC. Alternative schools are BYU, UTEP, Tulsa, Idaho, New Mexico State. BYU is unlikely because as long as they can set up 6 games with MWC teams, they will be fine with their current TV arrangements. Idaho and New Mexico State are also unlikely because they just don't have a tradition of being competitive.
The Sun Belt are scheduled to lose FAU, FIU, UNT and Middle Tennessee to the CUSA but is gaining Texas State, Georgia State, and UT Arlington (non football) to end at 9 football members. The Sun Belt should make every effort to keep at least three of these programs to get to 12 for a conference championship game. FAU and FIU should be taken as a set to keep Florida. UNT should be consider as a Texas partner with Texas State and similarly Middle Tennessee make a nice regional partner for Western Kentucky. If all four teams are kept the Sun Belt should look at New Mexico State to bring the conference membership to 14. Alternatively the Sun Belt could reach out to USF, UCF and ECU to got to 12 but this seem unlikely. With a presence in Florida and Texas the conference should be decent.
CUSA can pick up former members that left for the Big East that could not found membership in the Majors. These are SMU, Houston, ECU, Memphis, Tulane, and UCF. They are already at 12 so these will take them to 18. If Houston and SMU decide to go to the MWC, and if FAU, FIU, UNT and Middle Tennessee stay in the Sun Belt then CUSA should make an effort to take USF and or Navy. CUSA membership would be the current members, minus Houston and SMU, with Old Dominion, North Carolina Charlotte, UT San Antonio, and Louisiana Tech, without the Sun Belt additions, would leave the CUSA with 14, 16 with USF and Navy.