This game is like wow. When they come out with an expansion the first piece of gear you get at the new cap will be better than your best in slot from the last cap. Everytime an expansion drops it will be a completely new gear farm where nothing you had carries over. If anything you might be able to use AF2/3 etc as entry level gear for dungeons in the new expansion.

Oh and when it comes out, all the new raids will make people stop running the old ones.

At least, if the continue on track, thats what I bet will happen. I don't want this to happen, but that's how wow was. Every new expansion was a mad dash to rush through it before the next expansion came out and the previous expansion died.