They released a couple limited edition hats a while ago. In the announcement about it, they said those hats would never be resold and that once the stock was depleted it would not restock. If the wings were limited edition and an announcement was made about it, don't plan on spending your gralats on them EVER.

EDIT: I also want to make a side-note. All the "idle animations" (juggle, hoola-hoop, etc.) should not be bought unless in a Christmas gift. If you actually play the game as a game you should have absolutely no need to buy these and leave it up to Christmas presents to get them.