the MWC will never add San Jose State. San Jose State has serious financial and attendance problems, and may drop football like their California bretheren before them - Long Beach, Cal St. Fullerton and Pacific.
The reason the MWC teams left the WAC in the first place was that it became diluted with poor programs and too large, so that tradional rivals weren't always playing. Any expansion by the MWC will be done very carefully..
But it is coming, sooner rather than later. Logically, they can still maintain all of the "tradional" rivalries, with a 12 team conference, and get the benefit of a title game.
Fresno, Hawaii, and Boise are the logical teams to be added. The fourth would most likely be Nevada-Reno. Despite animosity between UNLV and UNR, Nevada would be the logical choice geographically, and also from quality of competition. Nevada is an up and coming program. None of the other WAC teams would be desirable to the MWC - it's almost Nevada by default.
That will leave the WAC with 5 schools (assuming San Jose State drops football). SMU, Rice, Tulsa, UTEP, LA Tech. They will merge with the Sun Belt football schools, and form a league that looks like this:
New Mexico State
Texas - El Paso
Louisiana - Lafayette
Middle Tennesse State
This is why Troy State hasn't been issued an invite to the Sun Belt - nor are they likely to. Louisiana - Monroe has also not been asked to join as a full member - they are having serious financial problems, and are unlikely to meet the new 1-A attendance requirements. They're future likely rests in 1-AA. This WAC/Sunbelt merger will likely either keep the WAC name, or have a new name altogether. They would lose their automatic bid in Basketball either way (there is a requirement to have the same 6 full-time members over a span of time... three years, i believe.... in order to get an automatic bid to the NCAA tourney. With only 5 holdover WAC teams, they wouldn't qualify). This will not be an expanded Sun Belt, as the non-football schools would not be invited to the party (South Alabama, New Orleans, Ark - Little Rock, etc). This would also seriously damper the 1-A aspirations for Western Kentucky and Florida International, as they would no longer have a league waiting for them to join.
MWC expansion by 4 would spell the end of the Sun Belt football league.