If you believe Dennis Dodd's old article about the TV money being equal for any new members (11 or 12), that suggests to me that ABC/ESPN/FOX want expansion to happen.
If I put on my tin foil hat, I think ESPN realizes that they're going to lose Big East football, which isn't a horrible thing, but it's a lot of content that disappears (and was willing to play during undesirable time slots). I think ESPN is all for moving ACC teams to the Big 12, but they would keep the distribution the same so as not to appear that they were enticing someone to leave the ACC for the Big 12 or actively make the Big 12 want to expand. The "all in" content package of the ACC means that they get a bevy of content for a crap ton of east coast schools that won't complain if they make them play on Thursday and Friday nights and Saturdays at noon on ESPNU and WatchESPN.
So, I personally think ESPN wants us to raid the ACC, they want the ACC to raid the Big East, and they want to leave a pile of crap for NBC to sandwich around Notre Dame. If the ACC lost, say, four schools and added two (UConn and Rutgers, UConn and Louisville, etc.), then went and added, say, Villanova, Georgetown, Notre Dame, and Marquette or St. Johns), they could have a 16 team basketball conference, 12 football members, and really, no one would have any issue with it because pretty much any school that's in the national consciousness would have a seat at the table. ESPN would only have to deal with five conferences instead of six, and they'd control all of the content for the ACC, every single bit of Tier 2 and Tier 3 content for the SEC, a huge chunk of the Big 12 and Pac 12, and a lot of Tier 1 Big Ten content.
I mean, at that point, if they negotiated with the A-10 and WCC, they'd pretty much have the entirety of NCAA athletics on lock down.