We sorta have that already in the form of virtual memory. The next step might be SCM (Storage Class Memory) where we use very fast NVM in lieu of SSDs or HDDs.

We sorta have that already in the form of virtual memory. The next step might be SCM (Storage Class Memory) where we use very fast NVM in lieu of SSDs or HDDs. Higher latency RAM would just be another tier in the memory hierarchy if it catches on.