I don't think any decision has been made in realignment, pretty much ever but at least in the modern era, without money as the primary factor. Especially by the B1G. So if Cal and Stanford cannot pay their way (which they cannot), they aren't B1G worthy. And it sounds as though Washington is borderline as best on the money front.
If I had to predict:
Notre Dame turns down the B1G knowing that they will have a spot when the ACC gets cracked open. There's no rush right now.
The B1G takes Oregon and Washington and stops at 18 for now.
The Big 12 takes six of the remaining Pac-12 schools - Stanford, Cal, Utah, Colorado, Arizona, Arizona State. Washington State and Oregon State go G5. Big 12 is also at 18.
The SEC waits to respond for when it can crack the ACC open, since there's no one on the table who adds to its cash either. They sit at 16.
Going further (totally guessing):
Whenever the ACC does get cracked open, the B1G adds Notre Dame, Virginia, North Carolina, and Duke.
The SEC adds Florida State, Clemson, NC State, and Virginia Tech. I'll guess that they also add Miami and one more (which could be from the Big 12 by this point), but I could definitely see them only adding one Florida school.
The Big 12 adds Pitt, Louisville, Georgia Tech, and Syracuse. Wake Forest and Boston College get G5 demotions.
All three conferences would have about 22 schools at this point. This sure feels like the end game of this stage to me. The next stage is whenever the Haves of the B1G and SEC decide to separate from the Have Nots within their own conferences.