As others have mentioned it all depends on what his potential caps are, but your improvement almost certainly won't be linear from year to year.
Walter Claude (
http://whatifsports.com/hd/PlayerProfile/Ratings.aspx?tid=0&pid=1783214 ) has been my best and most improved player. He came in to D2 rated at 482, and is currently up over 700 with a few games left in the regular season of his sophomore campaign. He also improved about 120 points his first season
He's starting to slow down (will still probably get to 100 in his sophomore season) a bit but still has at least 1 high high (in LP) that i haven't even begun to put minutes into so i'm thinking he'll be good to approach 800 before it's all said and done