S26 pretty much nailed it. Seeing a player develop after his 5th pro season is practically unheard of. He may increase a point or two in a few categories but players generally do most of their development in their first two full seasons.
My favorite HBD player, Slammin' Sammy Davis, and probably the only one I've ever called up before his 4th season:
http://www.whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=1660080As you can see, huge increase between S8-9, big increase between S9-10, and despite being called up in S10, a nice increase between S10-S11.