Bellarmine would probably prefer the A-Sun over the OVC or Summit-they get to renew the rivalry with Northern Kentucky (about 100 miles away), and Bellarmine thinks of themselves as a Southern school, not a Midwestern school (even if the "Notre Dame of the South" isn't that far from the Notre Dame in South Bend). I would expect the Atlantic Sun to add Bellarmine once NKU is far enough in the transition process to count as a Division I opponent. The Summit really should look at Missouri-St. Louis, who will be the largest school left in the GLVC.
What is interesting is that the Summit League would be down to 7 members who count as Division I for scheduling purposes if IUPUI leaves (Nebraska-Omaha won't be Division I until 2015). In the event of further losses, North Dakota is probably the first call, followed by UTPA, Chicago State, or NJIT. The Big Sky would likely accept a football-only membership from North Dakota given that South Dakota bailed on them at the last minute.
UMSL is not even thinking about an upgrade right now. First off, they are a commuter school with minimal facilities. Second, SLU and D-III Washington rule the college sports roost in StL with SIU-E not too far down the road. Plus I don't see the UM Board of Curators approving any such move with the current state of the economy in the state right now. Also, UMKC is a prime example of thinking they are "big time" when they have not even dominated the D-II level in any sport. Central Missouri would consider moving up to D-I before UMSL does.