I think the Pac 12 would want to add 4 teams if B1G and SEC went to 16 teams.
Not unless ESPN is directing them to take 4 teams to lessen payouts OU/UT have to make to exit the league or it allows them to get the Big 12 dissolved sooner. There are not 4 teams that add that kind of value to a contract.
I think its a better chance at this point the B1G takes 6 PAC schools with USC, UCLA, OR & UW part of the mix and some schools such as ASU/and or AZ, Utah, possibly Colorado need a home. But if they did this I wouldn't be shocked if the B1G tried to use KU and/or Co. as a bridge to the west.
The only way the B1G counters this move is by getting USC . Then to hope to possibly leverage that into getting ND at some time. If those two dominoes fell, maybe the B1G could even still lure OU & UT away from the SEC.
This all still sucks for ISU!