If NMSU joins the SBC, it will still be sending its teams halfway across the country in volleyball, women's soccer, baseball, softball, golf, and tennis. At least the WAC has some opponents in the Mountain Time Zone.
NMSU is right near El Paso, TX.
Seattle and CSUB aren't that close.
Neither are UTRGV, UMKC, and Chi St.
So really the only close (in terms of flight time) schools to them are Utah Valley and Grande Canyon.
On top of that the WAC offer virtually no travel partners (unless you count GCU/CSUB and UMKC/Chi St as travel partners.
And finally, everyone (except maybe GCU) is trying to leave the WAC for a more regional conference. Like ncaawhateverdude said, it's basically become the Great West 2.0 and if 1 school leaves, they'll be adding NJIT to the conference thus completing the coast to coast/lakes to gulf conference.
Looking at the SBC...
TX St, UTA, ULL, ULM, Ark St, and UALR are all reasonable for travel.
Yes, Troy/USA, GSU/GSU & App St/? are a bit of trip but with the travel partners help that out a bit.
I also think Texas A&M-Corpus Christi may not be long for the Southland given the recent direction o the conference. The WAC is really the only place the Islanders can go.
The Southland just added NOLA and added/lost Oral Roberts, and took a flier last year on UTPA/UTRGV.
TAMUCC isn't leaving the SLC, and the SLC isn't kicking them out (as they like being associated with an A&M system school) and I think the SLC may even double down on non fb schools like UTRGV (similar to TAMUCC, they likely want to associate with a UT system school) and possibly a D2 upgrade like Dallas Baptist (due to their baseball success and the fact that they don't have a school in DFW since losing UTA).
Fan of the Big 12 Conference, the Mountain West Conference and...