For example 2.5 years ago, my family bought a PC that had 256Mb of RAM, which we upgraded to 512Mb, and that was quite a lot back then, but a year later, most PC's were coming with a minimum of 512Mb, the majority with 1Gb.

So I think in 5 years time, we'll easily be looking at what we consider stupid amounts of RAM, though most likely for servers, not desktop machines. In fact I was just reading an article on Slashdot about "How To Use a Terabyte of RAM", it was more specifically for the Linux Kernel, however it provokes some interesting thoughts on what could possibly be done with that much RAM.