The ratings are quite impressive. However, the next conference realignment will probably come right around the end of the Geno era.
I think the most likely scenario for the Big Ten is adding Kansas and Colorado in the early 2020s (to take effect once the PAC and Big 12 GOR expire). They'll try to go after Texas but once it becomes clear that TX politicians won't let Texas come without Texas Tech, the Big Ten will realize that Colorado is the only other expansion option that makes sense. Denver is a growing top 20 market that would also bring the conference into another time zone. The "growing" part is key though since the majority of Big Ten states are either barely growing or losing population, a critical yet difficult-to-reverse situation that could have a serious effect on the Big Ten in the future.
Why would the Buffs leave for the Big Ten? More money, more stability, and political pressure. If Texas goes to the PAC-12, that would reduce the gap substantially between the PAC and B1G but who knows what Texas will do. Is Colorado willing to pass on the money and take the chance that Texas doesn't join the PAC? This would be happening at the end of the Grant of Rights so Colorado wouldn't be paying massive amounts of money to leave its current conference. Also, if CU leaves for the Big Ten, Colorado St would probably get invited into the PAC-12 so I could see Colorado politicians encouraging the Buffs to make the move.
As part of the agreement, the Big Ten would also take Kansas to make things a little easier for Colorado geographically. Both schools are AAU members and Kansas might be the best for out there for the Big Ten at the moment. The Jayhawks obviously bring great basketball and-just as obviously- terrible football. However, if Colorado can continue its recent success, the two football programs would balance each other out; Colorado would also help strengthen the Big Ten's western division in football.