ddr4
Nothx. You have to upgrade pretty much everything just to get ddr4. Normally upgrading everything would be ok, but ddr3 is still more than viable and atm ddr4 is more reserved for those with a fair amount of spending cash
However, if you have a stuff system and you have a large budget, then i say go for it. If your system is 4690k, a good mobo, and 8-16GB ram, then there is no point to upgrading.