BYU is going to the Big 12 as early as next year. Official announcement should be tomorrow.
BYU has had a competitive WCC rivalry with Portland for the past decade, particularly on the men's side, but have won 6 championships in a row. The BYU women have been dominant the past few under coach Taylor.
For BYU this is a slight upgrade in XC. Competing against Iowa State and Oklahoma State is tougher than Portland. But the rest of the Big XII conference is garbage, especially with Texas and Oklahoma leaving. The big upgrade will be for outdoor track, although the MPSF was competitive for indoor.