We had a huge sale on glass for the last two weeks, so there's a good chance most of them were snapped up in the sale. As far as restocking, it depends on what the manufacturer has on hand but it typically takes about two weeks once we place an order (which I'm sure has already happened).
I was wondering that as well. There was a HUGE sale on them over a month or two ago until everything ran out and the estimated in stock time on the product pages was for October 14th, but nothing came back. I hope they come back soon (and with more designs as was said in another thread somewhere) because it's been a LONG time since they were in stock.