I think the next / first Big 12 team (particularly in the North) that begins to develop a power running game will see the most improvement in the near future. Why? Because defenses are getting geared up for spread offenses and if a team is able to run right at opponents, they could be successful. I doubt the South teams like OU and UT will change what they're doing. The same could probably be said for OSU and TT.
In the North, ku and Mizzou have been the leading teams the last couple years by running the spread. Look for Mizzou to have a big dropoff (not just next year, but for the future). ku or Nebraska will probably win the North. However, I think over the long-term (3 to 5 years from now), somebody is going to line up in a power run game (even if it's not the option) and give other teams fits. I hope K-State is the team that does this (and wouldn't be surprised to see Snyder do this with an improved OL, Jarell Childs, and Daniel Thomas...and also because it would reduce the pressure on our passing game and shorten the game). However, I could also see CU, NU, or ku (if Mangino moves away from the spread post-Reesing) moving in that direction.
K-State and the other North teams are rarely going to out-athlete the UT's and OU's of the world. As a result, North teams will need to do what they can to have strong offensive and defensive lines, outmuscle opponents, and be assignment-sound.