Not really the new hot coral, as stated, the WWC bounce has been around for a few years. What really got it going though was the selling of a couple of WWC bounces for $6k to $7k last year. Once the suppliers see this they start looking for anything with a bubble hoping to cash in. You are now starting to see more shrooms with the bubbles at the $200+ price range. To me they don't seem to be selling all that fast. Most people still want the OG WWC bounce. Of course this also brings out all the people that like to complain that anyone that pays these prices are ruining the hobby. Then there was a recent article that claimed that intense lighting was what caused the bubbles which hasn't been proven. One guy actually claimed he had "bounce" shrooms for years in his tank and he could turn any rhodactis into a bounce. Of course proof was never offered and after looking at his other threads, I see he also claims he can get rocks covered in high dollar polyps such as the hallucination polyp for just a few bucks per polyp. Again he never shows any proof.
So I think bounces are popular right now but I wouldn't say "hot". Now the OG WWC bounce you could probably call it "hot". It was requested many times in the last WWC live sale, but they didn't have any.