There are 2 factors holding Ahman Green back. Unfortunately, those two factors are a) himself and b) his team, which are pretty important for most running backs. By a) I'm generally referring to his health; he hasn't been healthy since the 04 season. And b) refers to his offensive line and questionable situation, especially w/ 2 RBs behind him (Davenport and Gado) who can probably play and play well.
I wouldn't bank on him getting 1000/7, although those numbers are certainly possible if everything goes well. A more realistic projection might give him 800/5, w/ Davenport getting another 3-400 and Gado maybe picking up another 300.