The goal, it seems, is not to replace RAM or replace upgrades, but as a way to “temporarily” increase memory capacity for devices or to make swapping RAM upgrades easy:
IBM does not describe the invention as a replacement for typical memory upgrades, but as an option to increase the available memory temporarily and allow users to share RAM upgrades, simply by switching the module from one computer to another – especially in devices where RAM is not easily accessible, such as notebooks. According to the patent, the RAM box can provide up to four memory slots for every DRAM slot within a PC case.
Doesn't this seem counterintuitive? If you're going to open a case up and put a module in the motherboard, it might as well be real RAM. On top of that, one of the reasons RAM is located so close to the CPU is to allow it to communicate very fast via the motherboard. IBM doesn't mention how they plan to overcome obstacles like this, or how the RAM will be powered. Will it be carried across the data cable? What sort of speeds would be realized? Could external RAM come even close to competing with generic, bottom-of-the-barrel RAM that is actually seated on the board?
It seems like a rather silly idea, but perhaps it is too early to judge. I'd definitely like to see it in action. As it is merely a patent right now, and not any sort of production device, it may have far different applications than what we see now.