The X99 chipset is for Intel's Broadwell CPU coming in Q3 or Q4 2014.
Broadwell is socket 1150, the same as Haswell, but it seems that it requires a "9" chipset. That means people who currently have a PC with a Haswell CPU cannot simply install Broadwell because all current socket 1150 motherboards have "8" chipsets like the H87 and Z87 chipsets.