One theory I am hearing is once the 2026-2027 schedules are announced that PSU will play MSU, OSU, MD, Rut, USC and UCLA 3 out of 4 years.
So that's 4 quasi-rivals for PSU with MSU, OSU, MD and Rut where they play almost every year. Then throw in USC and UCLA almost every year to make up for not getting OSU every year.