Truth is ps2 did update. Its called a ps3.
I am not sure why new material not usable by ps2 would mean changing all the basic codes of the game. It is obvious that some of the new material in the game is already not easily, if at all, usable by ps2. Well its obvious if you play on ps2 or play with people who do.
There are things and areas that they just cant do. It wouldnt be much of a stretch to not make new material available to ps2 and not even pretend it is. They can still play the game but its time to start budgeting for new game device. (very hard to say since my best friend on game plays on ps2)