I think the move is to take 4 (utah, col, ari, asu) if you can... I don't think that is a done deal. If media companies do not want this to happen they will do something about it (similar to what they did to save B12 and stop the PAC 12 grabbing tx, ou, osu, and ttu about 10 years ago).
If we can do this, you put the pac in a really tricky spot long term. I think short term, they have a pretty fun league with 6-8 teams.. but would not last.
Once that is done, I think you wait unless wash/oregon want to come on their own. But I think you have to expect that in the next 10 yrs or so, the P2 will pick up these schools as part of a longer term structure - this would include eliminating current members of the P2 and creating a final structure that consolidates the top 24 - 32 brands. With Nike, I think oregon is on that list. Less certain about Washington.
I think the B12 should focus on becoming the nationwide structure for all 100 "left behind" FBS programs eventually consolidating all football schools into a single league that splits revenues evenly, defines rules for player and coach contracts and salaries.... basically establish the structure that everyone wants in college football.
It will be missing the top 24 to 32 teams, but it would be a much more attractive version for fans of college athletics. Who knows, in 25 years, maybe the 24 'brands' come crawling back from a failed semi-pro experiment and agree to join the B12!