I would be much more concerned about the capacity than the speed with regards to 2GB of RAM.
Programs are gobbling up more and more RAM these days - Chrome/Chromium
can use up to 1GB per tab (and I've heard of the browser using 5GB with only one tab open!). 8GB is the new standard, wasn't that long ago 512MB was.
Filling up your RAM leads to swapping to disk (pagefile on Windows) which slows processes down significantly and in some cases (if the "hand-off" isn't done in time) the system will become so unresponsive it will "freeze".
Versions of Windows that are 32-bit can support up to ~3.3GB of RAM; 32-bit Linux distros with a PAE-enabled kernel can support 64GB.
Since you mentioned future, starting with [some] Nehalem (i3/i5/i7) generation CPUs and newer, Intel replaced the Front-Side Bus with the QuickPath Interconnect which among other things means the memory controller is on the processor in modern CPUs rather than the motherboard. This means the bottleneck is the CPU instead of the motherboard chipset (though it is still a factor) with regards to the memory speeds possible.