Last year it took a little over a week for the entire expo to sell out. Given that the four-day pass sold out in under an hour of tickets going on sale, it's best not to delay if you want in. As in: go get your wallet right now and get it done before you move on to the next thing in your day. Fair warning.
Update: The official Twitter now reports that all badges have completely sold out. If you got a badge, we'll see you at the show!