I don't think they keep all their cash in bitcoins. It'd be too risky if the price dropped they'd loose a significant amount of money. They probably pay all their bills and some of their employees in fiat so they always need it on hand.
You are talking about a group of people who have so much faith in bitcoin that they've invested heavily into creating a significant online store that accepts ONLY bitcoin as payment. Think again:
Danny is exactly right.
I have no intention of converting my Bitcoins for USD.
Lots more big improvements to the stie will be coming soon too.