How long does Class A have?

Not long in general but if you have one and love it nobody will make you get rid of it. Also there will always be things sold as long as there are people who want to buy. But not many want to so expect to pay a premium for an increasingly niche item.

Greta has never pretended to be anything but a kid.  Her consistent message is to listen to the scientists.  Stupid science.

Linear powered class D module with a low power, class A input preamp section is the future.  High powered Class A output is like using a V8.  Inefficient and wasteful.

It’ll be around. Fear not.

Tubes are still in use, vinyl is till being played, class A will be around.

As far as the environment goes, wonder what is dirtier to make. A gallium nitrate chip, or a class A chip.

And what’s with these “men” tailing aim at a young girl?

Threaten easily, do we?

I seem to notice that equipment in the "hifi" world that sounds good, tends to stick around for a long time.  Vinyl records with the right combo of equipment sounds good, and fill that niche for carrying on the torch of nostalgia.  Tube amps survived solid state amps, hence they are still around, and again, the nostalgia of tubed equipment lives on.  Class A amps, they sound good, and just like record spinners, and tube amps, they have their foibles but most importantly, it sounds good.  A few decades ago, I bought a pair of Nelson Pass's Aleph 1.2 Mono Class A bruisers; still have them, and they sound wonderful to this day.  

In short, if it sounds good, and Class A amps check that box, then it will have longevity in the market.  The designs will get better, the transistors plus transformers will get better, the caps will get better, hence technology will help keep Class A alive.