The view from here is that the Patriots would like Green-Ellis to return and have a price in mind. The question then becomes if that price is attractive enough that it sparks Green-Ellis to sign before hitting free agency.
This is an area that I think the Patriots have generally done a good job at navigating.
They are disciplined in setting a price, but at the same time, keep a dialogue open with a player to let them know they want him back if what they are seeking on the market doesn't come to fruition. It's a strategy of letting the market dictate, and while it doesn't always work out, it preserves the relationship with the player while keeping the door open for a return.
This is where I could see things heading with Green-Ellis, in part because the team has young backs Stevan Ridley and Shane Vereen coming up the pipeline.
As for a possible market for Green-Ellis, the Chiefs could be on the radar, as Josh Looney writes on KCChiefs.com today. In 2008, when the Patriots signed Green-Ellis as a rookie free agent out of Mississippi, it was one of the top coups for the Patriots' personnel staff that year. Scott Pioli, now Chiefs general manager, was in charge of the Patriots' personnel department at the time.
Given that history, and Looney's breakdown of the Chiefs' running back spot, linking Green-Ellis and the Chiefs makes some sense.