And there's been rumors on Twitter and elsewhere that Oregon and Washington have applied to join the Big Ten too, but with no decisions yet.
An article making that prediction:
https://trojanswire.usatoday.com/2022/06/30/obvious-prediction-to-make-after-uscs-move-oregon-washington-will-join-big-ten/
If they get Cal and Stanford to join at some point as well, then Washington State, Oregon State and the four newest members of the Pac-12 will be left behind -- Arizona & Arizona State (both joined years ago to expand the conference from 8 to 10 teams), Colorado and Utah.
Then the 10 western schools would be:
USC, UCLA, Cal, Stanford, Oregon, Washington, Nebraska, Iowa, Minnesota and Wisconsin.
And the 10 eastern schools would be:
Rutgers, Maryland, Penn State, Ohio State, Michigan, Michigan State, Indiana, Purdue, Illinois and Northwestern.
Assuming such a super-conference would have divisions, which I personally think they should if the Big Ten indeed ever expands to 20 teams.