I think it would be silly of ND/Sony to simply discard the few additional and easy millions of copies this game can still generate, and have total credit for doing that because the game is arguably one of the best PS3 exclusives.
The videogame industry is an industry first and foremost, sometimes taking advantage of some easier things is part of the business. And no, no one is shoving it down your throat. Anyone who is going to buy is either a) a new-comer or b) a hardcore fan of the game that won't feel guilt for paying for the improved content again.