Yes. Cancel it. You at least want to wait until February to see if there is an iPad 3 announcement. I doubt there will be any shortage of Primes come February anyway, so what's the point of preordering one for delivery then?
Of course, on the other hand, tablets are moving fast. If you wait for the next big thing, you'll never buy one. But at this particular time, it looks like tablets are about to make the jump from "toys" to "laptop replacements". So wait.