The discussions in that thread pretty much explain everything.
There is probably a few unsold (new old stock) of the devices somewhere, no idea where or how many. The other question is who is going to do the repairs? I only know of a handfull of people around the world who do any real detailed Amiga repairs down to component level.
As for making new devices. The two main problems is that there is no known "internal" documentation on them. And re-creating some of the logic elements using modern FPGAs and the like would be extremely difficult to get working due to timing issues.
So in short, you'd better look after what you've got :-)
