What happened with the SACD format?

Yes, the plant has closed but production of SACD's will continue at the plants that do Blu-Ray.

Red book playback on the better transports and processors is getting so good that SACD is no longer the next step up in digital as it was in the past.

It is still alive.

Amazon has 4000 titles.

The format is 98% classical and Jazz, which is 2% of the total music market.

SACD production is mostly in Europe. The format is more popular there.

CD playback has improved in the last 10 years, and is very close in quality.

There are many SACDs released every year by different labels.

Though CD playback has technologically improved over the years, there is no way it can come close to SACD, IMO.
Simple test would be recording an LP to CD (44.1/16) quality and to SACD (DSD). The latter sounds much closer to the vinyl/analog.

Best wishes,
Alex Peychev
APL Hi-Fi

What happened to SACD? I don't think enough consumers cared about them for the big players to continue interest. They have become a niche market. One can argue about the superiority of the the format over CD all day, doesn't matter.

Sound quality and the things audiophiles care about has nothing to do with it. Manufacturers weren't making enough money to make them worth their while. Simple as that, economics; just business. Not enough numbers, maybe not enough margin?

Hypothetically, if SACD sales numbers were to suddenly skyrocket (which is highly improbable) those major players 'might' sit up and take notice. In other words, if there were money to be made. But I think that ship has already sailed.