1 serious point:
Maclin, Cooper, and Sproles can all go deep. They may not have the speed that Jackson has, but they are still good enough that they have to be accounted for. I don't recall Chip having to have a dynamic deep threat at Oregon to open things up. If the Eagles have enough viable options, which I think they do, and Chip picks the option that the defense is giving them, then I think they will do just fine.
I think Jackson will help the Redskins get to .500. I just don't think his absence will cause the Eagles to falter much. Yes, this is a homer opinion, but no moreso than you, fatness, thinking the Eagles offense will suffer dramatically without Desean.