SIU-E is probably going to officially get the Summit League door shut on them, as North Dakota and South Dakota have both been admitted to the Great West Football Conference effective July 1, 2008-I'd expect the Summit League to tie both of them up as soon as they count as Division I opponents for basketball.
With North Dakota State and South Dakota State already in The Summit League, North Dakota and South Dakota sure to follow, and Southern Utah also playing football, Western Illinois may be looking at joining the OVC for all sports or playing Summit League football since the Summit League would likely require its members to play football in-conference if it had six schools.
If Western doesn't leave the Summit League, this would also rip the Gateway back down to six schools (Northern Iowa, Missouri State, Southern Illinois, Illinois State, Indiana State, Youngstown State) and send UC Davis and Cal Poly SLO to become FCS Independents. Even worse, Western Illinois could find themselves playing a conference football game in California each year if the remaining Great West Football members become football-only members of the Summit League.
The only thing working against SIU-Edwardsville would be if Morehead State elevates their football program from the non-scholarship Pioneer League to the OVC, in which case the conference may want 12 for football. North Alabama would indeed be the ideal candidate, and they would allow Murray State to be in the same division as Southeast Missouri State, Eastern Kentucky, and Morehead State.
The Summit League can make a run to pick off Denver from the Sun Belt, or invite independent Utah Valley State into the fold.
OVC North: Southeast Missouri State, SIU-Edwardsville/Murray State, Western Illinois, Eastern Illinois, Morehead State, Eastern Kentucky
OVC South: Murray State/North Alabama, Jacksonville State, Tennessee State, Tennessee Tech, Tennessee-Martin, Austin Peay State
TSL West: North Dakota, North Dakota State, South Dakota, South Dakota State, Southern Utah, Utah Valley State/Denver
TSL East: Oral Roberts, Centenary, Missouri-Kansas City, Oakland, Indiana-Purdue Fort Wayne, Indiana-Purdue Indianapolis