I think the biggest issue for the Eagles is Jackson's attitude. He has a reputation for complaining about money and being a hot head. In terms of money, it's clear from the deals they're signing that the Eagles are very concerned about cap management, and don't want players to feel dissatisfied with their contracts. Attitude wise, DeSean can be a bit of a punk. Compare that to the culture the Eagles want, where Michael Vick of all people is admitting Foles deserves to start and handling it gracefully.
As a fellow Eagles fan, I don't think we have to talk about how shitty and miserable the last two Andy Reid years were. The egos. The laze. The bad attitudes. I don't know how to explain how miserable it was to a non-Eagles fan. I suspect that Howie/Kelly are very conscious of making sure the team's culture prevents something like that from ever happening again. I don't think they're pushing Jackson out the door, but if they can get good value for him he's gone.