Crucial, a company known for being in the RAM business, has
announced the release of DDR4 RAM. They even went so far as to make a nice little infographic describing the benefits of the whole thing. I don't want to think of how many hipsters they hired for that one, but it may not have actually been too many since the graphic doesn't seem to be tainted with "retro distortion and texture" effects.
The claims being made so far are lower power consumption, more speed, and twice the density. So for less power draw you can get twice the power on a single stick of DDR4, compared to DDR3. But of course, the architecture is entirely different so this means a complete upgrade of your system just to change to a new RAM standard.
New motherboard, possibly processor too depending on the socket, and a new mobo could possibly mean the need for a new power supply. If you haven't gotten a mobo that has USB 3.0, your upgrade here could mean you want a new case that has USB 3.0 capability with it. Either way, if you were looking to do a rig upgrade it appears that patience could be a virtue in this case.
Although Crucial has announced a late 2013 release date, there hasn't been any announcements from mobo manufacturers about conforming to this new standard. So you won't see any parts for it until 2014, and then give it about 6 months or so for bugs and drivers to be worked out; we're looking at a late 2014 time frame to go in on the new memory. And that is really an "at best" scenario. Unless, of course, you are knee deep into that early adopter thing.
This may also force an upgrade on people in the next couple years. As more manufacturers adopt the new standard the price of DDR3 will rise, as evidenced by what happened to the old DDR2 standard. Start your banking now, and know that despite all of this you will still have major game crashes at key times.