SMU, Tulsa, & Rice are leaving the WAC, citing "travel costs" as one of their reasons. This leads me to believe that Arkansas State, ULs Monroe & Lafayette, MTSU, & Troy State are not being seriously considered by the conference.
This leaves Idaho, Utah State, NMSU, & North Texas. Idaho is pitiful in football, so I don't expect an invite for them. It's USU & NMSU if the WAC wants to go with 9, or all three if they want 10 (or if LT leaves).
Go ahead and consider NMSU and USU in the WAC.
I don't see the WAC and SBC merging--the WAC is twice as powerful as the SBC (though that's not saying much). Think about it--the WAC has lost three of 1A's worst teams, and they'll add two or three of 1A's worst teams. The WAC is right back where they started, albeit with MWC raids looming. There's just no way the WAC and SBC will merge.
Yes, yes, yes Bayou-toot!
Look at it this way, the western WAC will not have to travel as far to play the conference dogs. Utah and New Mexico are closer than Texas and Oklahoma. If that is appealing add Idaho. If you want to add a higher quality program, and a "bridge" in the footprint out to La.Tech invite No. Texas. When the MWC steals Boise, invite them both. ;)