That's pretty much where we're headed, yes. In storage terms, it's actually probably more economical to only build up NVRAM fab capacity, too, since fresh SSD capacity is almost certainly not going to be about to recoup it's gigantic outlay prior to obsolescence now. The same will probably be true of RAM fairly soon too, and eventually HDD too.
In terms of it replacing actual RAM... well, unless you want to rethink the whole PC architecture to jettison the present role of RAM, we'll probably keep an at least nominal split between the two, for legacy reasons if nothing else. And as posters above note, not being able to clear the RAM without wiping your whole drive is a major downside which makes having the two split quite useful.