Well it started to show up in May/June of 2013. There were slides about the Intel 9 Series chipset (Both Z9x and X9x). We're going to get SATA Express across the board and it hinted at Haswell-E with DDR4.
In addition 2014 would only see a Haswell Refresh with new Haswell processors and Intel 9 Series boards that would not be backward compatible with existing 2013 Haswell processors and boards. Though this new 2014 hardware would be compatible with Broadwell.
Haswell-E would introduce DDR4 in late 2014 and Broadwell would show up in 2015.
http://wccftech.com/idf13-intel-demonstrates-haswell-e-ddr4-memory-x99-chipset-based-motherboard/
DDR3 was painfully expensive back in 2008 when Nehalem launched. I can expect it to be limited to Intel's HEDT platform and Xeon until 2015. I know DDR4 chips are in production right now.