Denver will probably try to hang around the Sun Belt for as long as possible. Commissioner Wright Waters is too much of a diplomat and gentleman to kick them out. Some of the membership might grow impatient, however, after a year or so of a 13-team, two division, conference where Denver sticks out like a sore thumb.
The Big 12, Pac 10, WAC, MWC, and Big Sky will not take Denver. No football. End of story. The WCC and Big West are based completely on the West Coast, mostly in California. Neither of those leagues will take Denver. The MVC already has 10 teams, and none of those are in the Mountain Zone. Distance and history there.
Only one conference has a reasonably ready-made "footprint" for Denver. That's the Mid-Con, a league which wanted Denver when it first moved up in 1998. With the exception of Chicago State and to an extent IUPUI, these are not "commuter schools" as most have nice residential campuses and good academics.
Oakland & IUPUI
Valparaiso & Chicago State
Western Illinois & UMKC
Oral Roberts & Centenary
Southern Utah & ... Denver
If Southern Utah can ever get into the Big Sky somehow, the Mid-Con could add Northern Colorado (which really wants to join) and give Denver an even better travel partner. This move would also tighten up the league's geography just a little bit. Joining the Mid-Con could actually be a very good thing for Denver.