Other than Metro State, which is already larger than many Division I schools, there is only one other RMAC school that makes sense for Division I, and that is UC-Colorado Springs.
The problem is that if anyone departs before Grand Canyon's transition is complete, the WAC trips the probationary period again. It takes four years to move to Division I, but the probationary period for the conference would be two years. The WAC may be waiting on C-USA to replace UAB before it can make a move. If C-USA taps any Sun Belt school, and the Sun Belt invites NMSU, the WAC has no choice but to invite an existing Division I member - NJIT might not be an option by the end of the academic year given the Highlanders' moves to join America East.
If NMSU leaves, I'd expect UMKC to go back to the Summit, UTPA heads to the Southland, and Bakersfield is rescued by the Big West.
If the WAC survives, or if nothing happens above them to trigger realignment, I'd expect Metro State to join in 2017. Four more years down the road I'd expect Western Washington or a CCAA school to join.
Metro State/Utah Valley
If that holds up to 2025 I'd expect to see another Texas school added, which would push Utah Valley into the Pacific Division. Another California school gets added to take the WAC to 12.
I am not certain the Southland would add another non-fb school, since they have an even number(2) currently. If UTPA started fb in a few years...I would imagine that it would still behoove them to stay in the WAC/Indy rather than trod through the FCS levels waiting for a call up(ie: Charlotte landing in CUSA then bringing fb up quickly). But, that scenario contains a lot of "IF's" and quite a few years to get up to speed.
Also, hard to say if the Big West and Summit would welcome any other WAC schools. It could happen, but seems doubtful since it hasn't happened already.
How about Regis U. as a partner to Metro State and/or UCCS? Regis is similar in size/money to Seattle...and is located in a major metro area. With two or three schools in one area...travel could be easily reduced by a large degree for the whole conference.
There is also the 'whipping post' effect. So, all current WAC members could chalk up a few extra wins each season while the newbies begin to establish themselves. As long as they kept their OOC games respectable...their RPI wouldn't dip too much. If they get these(or any) schools in now...they could be fully up to speed by 2019. And that seems to be better than sitting on the edge of extinction for an extended period of time.
You mention schools from Texas. What schools did you have in mind?