According to memory maker Crucial, DDR4 RAM will be available for the first time by the end of this year.
The new technology will offer several advances over the current DDR3 standard, running at 2133MHz and offering 300% density. The smallest size will start at 4GB and single slot sticks will be able to support up to 16GB.
The power usage will also be significantly lower, reducing it by 20% compared to the current DDR3.
You will obviously need to get a new motherboard to support DDR4, it also won't be very cheap, with it set to become the standard in perhaps 2015 or later.
Source: MCV UK