Most people do not mean forever. In the tech world, forever is a decade.
They will make more RAM due to demand and competition... but it takes a long time to ramp up and it is expensive. This will feel like forever.
Furthermore, AI wants the best RAM and not everybody is making the best RAM. So, when DDR6 happens, it'll be possibly out of consumer hardware for a longer delay and priced higher for longer obviously. The bubble will burst but it doesn't have to be like other bubbles. Many view this as existential not just 1st to market; not everybody is betting the house on short term breakthroughs and they won't fold when others' pyramid schemes fail... again, some are racing to own the Terminator 1st; as long as they don't outpace their ability they will keep going.
RAM prices getting cheap after a market correction, will be a short blip. It'll go back up. Eventually, we'll level off but likely to a more rigged market of price fixing than we already had. Corruption has been on the rise if you've not been paying attention.