I've also read about a possible come-back. "it is not completely excluded that Astia 100F might come back one time" (see this thread). That sounds rather iffy, so it's safe to assume that the Single-8 is old stock Astia.
Hm... which slide film are you using now? Will that be the next one to go?...I did a slide show at a party over the weekend, which included some Astia slides. I commented on loving the film but it's been discontinued. Several people commented that they could see why I liked it. (Of course then I moved on to E100G and really liked it too....)