I really can't see teams like Washington, Oregon and Stanford not eventually being invited.
The Big Ten and Pac-12 have been linked to each other since 1947. I think they want to keep an affiliation with the best of that conference and they can do that - AND - corner some major TV markets. Those three teams would/will allow the B1G to own not just California, but the entire west coast, encompassing the entire pacific northwest. Heck, those five schools basically give you ownership of the US west of the Rockies.
It also allows USC and UCLA to have a pod of teams they can play on an annual basis. Those five teams can play each other every year and then can schedule their 3 non-conference teams and have them be schools that are in Pacific time zones as well. That would leave only 4 games where they'd be playing current B1G teams and the conference could space those out so they're not hit too hard by the travel and timezone issues.
I think they're eventually going to go for 24, not 20. This could allow for the additions of Cal, Utah or BYU. Probably not all three, though, as I imagine they'll want to grab a few teams in the North Carolina/Virginia area.
I also don't get the suggestion that Kansas would/should be considered. They bring nothing to the table outside of basketball and these decisions are football driven. Sure they allow you a foothold into the KC metro, but IMPO that isn't enough to have them above other schools.
They'd be much better off going after Duke if basketball is part of the argument. The Blue Devils are the "Alabama" of hoops and they'd offer a much better TV market and recruiting pipeline for the conference. Their academic reputation is also a nice bonus. And unlike Kansas, their football team is actually respectable.
I think the ideal 8 additions to bring the B1G to 24 are Notre Dame, Stanford, Washington, Oregon, North Carolina, Duke, Virginia and Georgia Tech. The first 7 were pretty easy for me, I settled on Georgia Tech because it gives you Atlanta and a presence in the south for recruiting. They're also a strong academic school and competitive in several sports. Admittedly, I can see an argument for a few schools in their spot.
I wonder if the B1G will pay the cost of getting their desired ACC teams out of their GOR contracts, or wait and see if the SEC starts grabbing teams like Clemson, Miami and Florida State and watch the ACC simply crumble (which I think is inevitable anyways).