I wonder if there's a bit of a chicken-and-egg issue where there wasn't much that demanded 10x the RAM, so there wasn't much pressure to develop more or increase production to support it at consumer prices.
There's wayyyyyyy more demand for memory generally now, so assuming it's not a demand bubble that pops rapidly, I'd expect the new normal to end up at a much higher baseline. 512GB would be 4x greater than today's max, so even with the relatively slow last 10 years development pace, give it five years max?