I'd bet on DDR4 RAM when skylake goes in.
I don't know much about that, but it doesn't seem like that'd be too big of a deal for me:
« [C]omparing DDR3 and DDR4, neither was a clear performance leader. The difference between DDR3-2133 and DDR4-2133 was negligible in a number of applications, ranging from Handbrake video conversion to half a dozen different games. DDR3 was slightly faster about half the time, and typically only a few percentages points separated the two memory types ».