It's still running. I submitted an article last month about how Micron was buying a facility that had actually just opened quite recently and was apparently producing DDR4 to refit it to make HBM; faster than building a new memory factory from scratch.

But as I point out in another comment in this thread, my guess is that this is more about being able to tap the already-manufactured used memory market. There's a lot of DDR4 already in computers, and as those computers get disposed of, as long as it's not thrown out and goes back on the market, that makes DDR4 available.