Based on what they said at CES (which was january of this year, so it has been a bit), "server stuff" was getting DDR4 late this year, with "desktop" DDR4 coming towards the middle/end of 2014.
LGA2011 and whatever socket Haswell-E is on are a semi-server platform, generally included in "server stuff" but not always.
It's possible that DDR4 got pushed up to the Haswell refresh, which would explain the new socket.