Is there a glass ceiling for cable technology??

As long as cable manufactures employ marketing and PR firms, there always will be advancements.

Any cable will have a different on your equipment, so anything they put out can sound different than the cable they produced before no matter the brand. Never was a ceiling just impendence effects between 2 pieces of gear and then the wire connecting them. This why you have to try before you buy, it a crap shoot on the sound out come. Yes every year a new name to keep the product fresh and us buying them, now a new cable weekly comes out, a very money making business as a side line for many.

"There's a well-heeled sucker born every minute."
Many of these suckers are "audiophiles."

I was under the impression that the glass ceiling was reached decades ago by Monster Cable.

Of course you could just leave out the word "cable" and ask if there is a glass ceiling for audio technology in general. Since so many seem to enjoy analog and vacuum tube technologies over digital and solid state technologies, one could ask if technology in general is even moving in the right direction, let alone hit a glass ceiling.