The Big 12/SEC expansion had a lot of interest and the ripple effects are now being seen in the G5. Everybody is raising lesser conferences and some are even being turned down. Here is the current movement:

• AAC: They are losing UC, UCF, and Houston to the Big 12. They initially tried to raid the MWC by adding Air Force, Boise State, CSU, and Sand Diego State to replace what they lost but those teams said no. Now the AAC will raid conference USA and are rumored to be taking Charlotte, FAU, North Texas, Rice, UAB, and UTSA.
• MWC: A successful defense of their top 4 programs was huge for the conference because there are simply no other west coast D1 football programs to replace those that would have left. The MWC considered grabbing the Texas G5 schools but AAC took them first. 
• Sun Belt: Potentially the biggest winner in all of this is the sun belt. For a long time the bottom conference in all of D1 and CUSA denied an attempted merger a few years ago. Now they are sniping Marshall and Mississippi State from the remaining CUSA. They are also considering adding James Madison and Old Dominion.
• Conference USA: The biggest losers of expansion are doing everything to try to survive. They are going all out for Liberty and James Madison to stabilize the conference and convince Marshall/Southern Miss to stay. This conference may not exist if they can’t keep the few teams they have. 
• MAC: Very likely going to stay out at 12. Very solid market with a good TV market due to their willingness to play midweek games. Would be interested in Marshall+WKU but the Sun Belt would be a more likely move for those schools.