My guess is that people are finding out it's amazing and buying up all the copies. You were Just late to the party(haha, pun totally intended).
Seriously though, there is no reason to think this game is going out of print. Sales are good, gamewright looks stable and there aren't any pending legal issues to bog it down. Unless you are buying a birthday present, you can probably wait a couple months. I'm sure they'll want this on shelves in december.
Considering that it's Gamewright, it should be available again fairly soon. If it were Z-Man then your only recourse would be to make sacrifices to as many deities as you could think of. Then you might find it in a year.
I was wondering the same thing! A couple months ago it wasn't available anywhere in Europe and now it is out of stock already and all I can find is being sold for crazy prices. I hope they will release more copies at some point soon.