There are two theories as to the BBI endgame.
1) Uhuru is entertaining extending his term through a new constitutional dispensation - Prime Ministership.
2) Uhuru is stringing along Raila so he can finish his term without makelele & also doesn't want to become lame duck so will play the game.
I am inclined to believe #2 is happening here. To change constitution Uhuru would have to engage politically. He has disengaged - and is not ready for a referendum. Without a referendum - any changes to laws or constitution will be cosmetic. BBI will just be smoke and mirrors.