Crucial are rolling out the next-generation of memory, and it might be available as early as the end of 2013. Crucial has a promo up on their site for the new DDR4 memory, and there are lots of fancy graphics showing you just how much faster it will be, and how bad you will feel if you still have DDR3 instead of DDR4.
DDR4 will be double the speed of DDR3, which came out back in 2007. It will also use 20% less power, and each stick of RAM will be able to have double the amount of memory on it.
It could be a few months before this becomes widely available, but if you had plans to build a new PC you might want to wait until DDR4 is out, at least to see if the prices of DDR3 go down.