Pure speculation but trying to keep some sense of reality for the B1G.
USC and UCLA are now in the fold. The expansion is done for the time being statement is true but by the time you say the phrase "for the time being" the time being has passed. I think B1g still has eyes out west. Stanford to me is a logical partner for NDU. Another private school with elite academics, great olympic sports and the San Fran TV market. Gives the B1G great private academics with Northwestern, NDU, Stanford and USC.
I think Oregon is in. Phil Knight and Nike aren't sitting around to be left scrambling.
So, if you have Stanford, NDU and Oregon, you need one more. For me this comes down to Arizona or UW. Do you want the Northwest or the Southwest. You can convince me either way but I keep going back to would you rather road trip to Phoenix or Seattle? Where do B1G fans go to retire? Which location has better opportunities for bowl games in December and January?
So, I think the end game is NDU, Stanford, Oregon and UA. If NDU is a no go, I think you can still put in UW and have a Washington, Arizona, Stanford and Oregon grouping and still make it work.
EDIT: Even though I think we are well past the charade, Arizona, Washington, Stanford and Oregon are all AAU members.