Frankly, it's a bit weird that it's taken so long for the old paradigm of these clunky memory sticks you plug in to a bunch of slots on a motherboard to go away.
It's a product of the technologies used. A lot of people seem to think that RAM is slow because it's far away. This is incorrect. RAM is slow because sense amping a DRAM cell is slow. It's far away because when it's so slow to start with, tagging on +20% transport latency does not hurt you enough to make the advantages of upgradeability and commodizability of the DIMM modules to go away.
So, DIMM modules as they are will go away when we move from DRAM to a better kind of memory, with less access latency. There are a lot of new kinds of memory tech "waiting in the wings", ready to take over if they ever get close enough to plain DRAM in cost per bit. However, DRAM manufacturers have managed to cost-reduce fast enough that it hasn't happened yet.
Personally, I think that we are actually pretty close to revolution on this front. The new memory techs still aren't cheaper than (or all that close to) DRAM per bit, but as the need for more memory hasn't kept up with the advances in production, it doesn't matter as much as it used to. RAM used to be a fifth of the price of a computer, now you can get 8GB for <$40, and that's more than good enough for most real uses. So even if the price can't keep up, what if in 2-3 years you can get 4-8GB of
really fast ram for ~$40 instead of getting 16-32GB for ~$20? Assuming the rest of the system is updated to make use of it, that would probably help real, user-noticeable speed more than all the advances in CPUs in the past 5 years or so...
( If someone is interested, the layman explanation of why DRAM is slow:
Generally, the biggest reason that circuit elements get faster with shrinks is that as geometries get smaller, there's less distance to cover, there's less conductor to load and in other ways electricity just has to do less for the same effect.
DRAM works by having a really small capacitor that you stuff electrons into to wait until you read from them. On a read, you release these electrons to your sense amps, amplify the signal to something useful, pass it along, and re-store it in the cap.
The problem is that as you move to smaller geometries, the amount of electrons you can store in the capacitor goes down, to the point that reliably sensing the signal from them is really very hard. You need to have long chains of ever more powerful amplifiers to turn those initial few hundreds (soon few tens!) of electrons into a real current that can be sent across a wire, or even passed to the nearest normal transistor. )
