Well, a few questions that kept popping up here about arena points have been answered.
From the Euro forums:
WoW-Europe.com Forums -> Wrath of the Lich King Arenas
Arena points will go poof once you hit 71, as will your teams. You will be able to make new teams and start fresh at 80.
However, it seems that if you stay at 70 you can keep your teams and keep doing ranked matches. There just won't be any new rewards.
They also say that they will be adding two new skirmish brackets so you can test out your new skills in the arena as you level.
Most importantly - New arena sets won't look like raid sets anymore!!! Yay!