The main guy behind the CST decided to retire and go fishing. Sold the IP to PI, which seems to have stopped production.
Edit: I haven't been paying attention, but last activity I noticed regarding CST was a Massdrop buy for the optical trackballs last year. Had I known with the benefit of hindsight that they'd suspend or stop manufacture, I would have bought one. I had an opto-mechanical model for about five years, and it was great, much more satisfying to use than a mouse. Eventually it developed some issue with one of the sensors though, so I dumped it.