> SSD speeds will probably continue increasing, so removing RAM will take us about 20 years back to the past

I think you significantly overestimate how much they can reduce latency for SSDs. Keep in mind, even a 80286 from 1982 had a memory latency in the 200ns range[1].

[1]: https://cacm.acm.org/magazines/2004/10/6401-latency-lags-ban... (view PDF, table 1)