The Big 10 (down with the stupid B1G name in light of potential realignment) seems to be pretty quiet on the realignment front, with Kansas making overtures to join the conference, but the conference itself only putting out minor interest in the popular PAC schools (namely USC), at least publicly.
The thing about USC or a partial addition of PAC schools (call it <6) is that it doesn't seem feasible for scheduling considering the geography. Furthermore, while I'm not opposed to the idea of merging the PAC and Big 10 and having a "Western/Pacific Division", I'm surprised the Big 10 hasn't gone after certain ACC programs that are much closer geographically, good fits culturally, and may be solicited by the SEC. I'm thinking primarily about UNC, UVA, GA Tech, VA Tech, and to a lesser extent NCST, Wake, and Duke.
The ACC has a handful of schools that are clearly northern, or at least not-Southern (1. BC, 2. Louisville, 3. Notre Dame, 4. Pitt, 5. Cuse), 2 that are clearly in the South (FSU, Miami) and the rest are all clustered around NC (1. Clemson, 2. Duke, 3. GT, 4. UNC, 5. NCST, 6. UVA, 7. VA Tech, 8. Wake). Adding 2-4 schools (e.g. GT, ND*, UNC, UVA) from that mid-Atlantic cluster to tap into the TV markets (DC is 7, ATL is 10, Charlotte is 21, and Raleigh-Durham is 27) and have better access to recruits from the talent-rich areas of the DMV, Norfolk/VA Beach, and the stretch between ATL-Charlotte (aside, is there a specific name for this area, or is it basically ATL+Research Triangle) could really strengthen the conference without breaking the alignment model to pieces.
Thinking a bit bigger, if the Big 10 wanted to take a lead role for the non-SEC schools, they should add an "ACC Division" and then do the same for the PAC, and have 4 divisions spanning the nation. Although if that happened I would hope the Big 10 would look to shed some dead weight in the transition (looking at you Rutgers and Nebraska).
*Notwithstanding the obvious importance of ND to realignment, to hell with Notre Dame!