Either in a John Elway with the Broncos type move where he becomes the GM that replaces Grigson or some other capacity that gets him back on-board in the organization and could eventually lead to the GM spot.
There is also speculation that "if" Jon Gruden were to be lured out of the booth and back into coaching, it would be to the Colts because he has said a couple times now that the only QB he'd return to coaching for at this point is Andrew Luck.
The idea of Manning as the new GM and Gruden as the head coach excites a lot of fans in Indy, from what I've read and heard. It would certainly be interesting at the least.