Why would they need another school? The WCC had 10 members before Gonzaga announced they were leaving. Naturally, that raised concerns that Saint Mary’s might be next, leaving the conference potentially down to nine — or even eight — in the near future.
To address that, the WCC announced that UC San Diego (its only public school) and the University of Denver would be joining. If Saint Mary’s does leave, that would bring the total back to 10 — the same number the league had before Gonzaga’s departure. None of the remaining WCC schools would add real value as Olympic-sport-only members to an FBS-level conference anyway. I think WCC is done with expansion at this point.
After all of the conference movement, I see the WCC and Big West as peer conferences athletically. When the WCC had Gonzaga and St. Mary's (assuming they leave) they were clearly the more dominated conference. Now the only difference is the NCAA credits that Gonzaga and St. Mary's leave behind. Very much like Creighton and Wichta State leaving the Valley and the Valley had a much stronger remaining bench of schools. They are simply going to become single bid conferences. In today's environment, the gap in money is too large to overcome.