Stanford and Cal's sports line up pretty well with the Big 12 sports offerings, better than the WCC. And, in the Big 12, Stanford and Cal would be playing 4 schools previously in the Pac 12. I just can't imagine Stanford and Cal, 2 academically oriented schools, sending their teams across the country to play ACC schools.
I think the order of preference for Cal and Stanford is:
1) Big 10
2) Big 12
3) Independent in football/WCC
4) ACC
Financially, I think the ACC can make Stanford/Cal/SMU work, but I don't think Stanford/Cal want to join the conference.