I've read way too much on this and probably 99% of what I have read is from people that don't know any more than I do....with the being said, I think the B1G/Fox wants FSU & ND (who both increase the per school B1G payout) and thats it. They would like UNC too but I think they are destined for the SEC.
IMO B1G will stop and be very happy at 20 (which is a big league but much more manageable then if you go beyond 20). At 20 schools you probably go to 10 conference football games and play everyone once over 2 years and your 'rival' twice and play in every B1G stadium in a 4-year period. In basketball you play 20-game league schedule, play everyone once and your 'rival' twice. All the non-rev sports probably try to be a little/lot more 'regionalized' when possible.
As to people that probably know a lot more than I do, I see the FSU on3 site admin put an update out on Wednesday that had a few interesting updates on if the SEC is still in play for FSU and the B1G having little interest in Clemson.
Myself and...
www.on3.com