If Crucial Memory's promotional page is anything to go by, we could expect DDR4 RAM to be released next month. But, this will require new motherboards, and even if you did that, is there a benefit?
Yes, and it's quite the improvement, and a bigger improvement than we had moving from DDR to DDR2, and even DDR2 to DDR3. DDR4 memory will use 20% less power, deliver speeds of up to 100% faster, and is 100% denser than its predecessor. Most DDR3 is around 1066MHz, but DDR4 kicks things off from 2133MHz, which is a huge increase.
Another benefit is going to be the amount of RAM per stick, with DDR3 seeing 1Gb when it was introduced, and while we have more per stick now, DDR4 will have a sweet 4Gb density. This means we should see much higher GB kits of DDR4, where we should hopefully see kits being at a minimum of 8GB, although I'd like to see 16GB. We should finally see a world of 16GB per module, which will be great for 64GB kits when Haswell-E arrives.