https://www.xilinx.com/support/document ... n15006.pdf
Unless there's a document superseding this one, they've not been manufacturing them since the start of 2016. So stocks will definitely be dwindling.
With regards to aliexpress, i have a feeling that the stocks of various stores on there are shared across resellers listed in China. So when you buy from one you essentially buy from all of them - the same way they work on ebay. Still, i think ali/ebay's only customer will be the hobbyist, and I can't see tens of thousands going like hotcakes.
John