I actually think it would be MORE of a selling feature that would incline people to go out and buy the newer version knowing that all their career efforts would not be lost.
I imagine there are many people out there that are always a bit reserved about buying the newer version because they have vested so much time in the previous year's game with their frachise and dont want to have to start it all over. Hey , I think this should be a standard feature. If they have the ability to allow you to import your NCAA graduates into Madden, they should certainly allow you to import your older dynasties into newer versions of the game
So they've added new attributes, I'm sure in this day and age, they can design some sort of reasonably intelligent conversion algorithm that would realistically import into the newer game and generate these new player ratings along with the old ones...c'mon gimme a break!