The Big 10 can add Kansas and potentially work around the "Grant of Rights" issue. A grant of rights does not prevent a school from moving. It only prevents a school from bringing its TV rights with them. So if Kansas left, all the Kansas games would remain property of the Big 12 for next dozen or so years. Or at least the rights Kansas granted to the Big 12. Remember that in the Big 12, that's only Tier 1 and Tier 2 television rights. Kansas retains its rights to Tier 3 sports.
If Kansas went Big 10, it could provide no Tier 1 or Tier 2 inventory to the Big 10 until its grant of rights expire or the grant of rights was bought out. However, it could grant Tier 3 rights (or buy out whomever owns them) to the conference. The Big 10 could then take the Tier 3 stuff and stick it on their network. While the main content providers might not likely pay the Big 10 any more money (since they'd get no more content than they already have), the Big 10 Network can increase its profits. The BTN would have Tier 3 Kansas content, not to mention all Kansas road games playing other Big 10 teams. The thought is that people in Kansas would still want to see these games and the Big 10 could still charge higher carriage rates to people in Kansas to keep the channel. So in reality, you'd only be missing around 6 football games and around 12-15 basketball games per year. Those games are still worth good money, but aren't the end all, be all of television content. The bottom line is that the grant of rights could be worked around if you really wanted it to happen.
I just don't think the Big 10 cares that much about Kansas to bother doing that.