As a Bill:
Travis Henry: 3,849 yards rushing, 691 yards receiving, (4,540 total yards), 29 offensive TDs
Willis McGahee: 3,365 yards rushing, 503 yards receiving, (3,868 total yards), 24 offensive TDs
CJ Spiller: 3,321 yards rushing, 885 yards receiving, (4,206 total yards), 17 offensive TDs
LeSean McCoy: 3,300 yards rushing, 1,096 yards receiving, (4,396 total yards), 27 offensive TDs
Barring a serious injury or trade, he'll be above all of them by mid-season next year in rushing alone. He's only 29 and has 2 more years on his contract. Add one more year onto that and he'll have played as many seasons in Buffalo as Philadelphia. Projection, I know, but possible.
No one is arguing any of those Bills you mentioned (especially the 2 safeties being here only 1 year) should go on the Wall. When people think of the end of the drought they are definitely going to remember him salting away the Colts game.
Not saying he's there now, but I do think he will be able to get there.