I couldn't even really tell you, I think most are long gone. We know a few "die-hards" but most of their children are out.
@Christian, what you mention about Katja's congregation is happening in my Mom's congregation. Several couples have grown children they "can't speak to" (again, of course, they could if they wanted to). A couple of these are getting really old, and yet they stubbornly hold to the rules even though they could really use some help from their adult children. Three other couples have grown children that are still JWs, but get no help whatsoever. So it begs the question, who will take care of these ones? The congregation is just worn out, poor, and not attracting any "new blood". At the memorial the thought crossed my mind that it was really a "mothballed" congregation, really sad. Nothing at all like its "glory days" in the 80s and early 90s.
The extra pressure of helping/managing elderly parents (that everyone in my generation is feeling) might just push this group "over the edge". Time will tell. Apparently the GB failed to plan for that.