Have they made any kind of public announcement? I couldn't find anything.

Yes, this is very sad, but there just aren't enough of us old-time balsa builders left to keep companies like Sig going (and I would guess the margins in the ARF market to be so razor thin as to make it hard to keep going too). This is the same dynamic that ultimately led to the demise of TF and Great Planes kits. That does not mean the end of the hobby, it just means the end of a particular era. I get a lot of RC related posts on my IG feed and keep seeing more and more sophisticated foam builds and 3D printer builds and all sorts of innovation going on. It may look different (and may not appeal to some of us old-timers) but it has the same soul.