If you're like me, you ordered the new iPad as soon as Apple's servers allowed, and you are waiting patiently (or perhaps impatiently) for it to arrive. Now is the time to think about protection. In fact, I sold my old iPad at SellYourMac.com
and got full price because it was in such good shape. I keep my iPads and iPhones in cases pretty much full time and they look brand new.
Now keep in mind, the new iPad is slightly thicker and heavier than the iPad 2, and has a bigger opening for the camera, so there's a chance your old case might not work.