I really don't theink the S3++ had different chips, in terms of design, compared to the S3. They were no doubt better, and clearly the S3 got a rough start, but the chip design is virtually identical. Maybe somebody more in the know could comment, but the S3++ more like a "fixed S3", than a V8 version compared to the V6 version to use the car analogy. Once the S3++ was out, there were no more S3's available, except on the used market.
I don't know if we ever really saw much on the S3++. Was it just bulk in China sold? I could be wrong on that but I was thinking it was not offered to all.
If you look at S5 they designed to ship, with plastic and not full metal like S3. I think it's likely S7 will continue that trend. But as far as timeline I have no idea.
On S4+ there seems to be so many different stories on this forum, I don't know what to believe.