I'm wondering when the first system without any Ram at all will appear. Current SSD speeds already surpass SDRAM speeds from ~20 years ago. While it will probably take some more time to reach DDR(2) speeds (let alone DDR3), I could imagine that entry level machines would do away with main Ram once those SSD's have become sufficiently cheap.
Instead all operations would be executed with the SSD doubling as main memory. Surely there are some implications, but still ... No more data transfers from storage to main memory, easily 128GB+ main memory (yes I know - who actually _needs_ that

) and most of all: reduced footprint of the PCB and (potentially) reduced system cost (for the producer).
I'll go out on a limb and expect the market arrival of such systems within the next 5 years. I'm pretty sure they are already running in some labs.