No chance is probably too strong an assessment. While the Big 12 rakes in roughly $20m per school (
http://espn.go.com/college-sports/story/_/id/8346345/big-12-announces-media-deal-abc-espn-fox), the Pac-12 rakes in just about the same amount (
http://collegefootballtalk.nbcsports.com/2011/05/04/pac-12-officially-announces-landmark-media-deal/). The difference is not dramatic, and the numbers suggest that the Pac-12 gets almost $1m more per school (insignificant a difference in it of itself for sure). However, the media rights deal the Pac-12 could get with Texas alone in its footprint is massive. Adding Oklahoma brings that market into the equation and gives the Pac-12 control of one of the biggest rivalries in college sports. The raid of these four Big 12 schools came perilously close to happening in 2010 (
http://espn.go.com/college-sports/story/_/id/6998751/pac-12-conference-decides-expand-further).
Kansas, if the opportunity presented itself would jump at the chance to go to the B1G. The B1G pays out $5m more per school (
http://espn.go.com/blog/bigten/post/_/id/76205/big-tens-tv-revenue-keeps-climbing), and projects a higher payout when its rights come up in 2016. The Big 12 has only 5 states in its footprint, and with three of those states have multiple members, the opportunities to grow that pot are limited. Especially if the Pac-12 came calling again, there is no benefit to sticking around with 6 schools when stability is so quick to attain.
The ACC has reason to remain concerned because two powerful conferences flank them. The SEC would love to get into NC and VA. The B1G would love to reach into those markets as well. However, the UNC and UVA talk to the B1G seems to have died down for now. Both see themselves as "Southern" universities and don't want (at the moment) to go to the B1G. However. if the SEC came calling and ripped two teams, the B1G would respond, and the Big 12 lives to fight another day with new members.
I'm not saying that it is going to happen that way, but the conference does have reason to sweat.