Intel recently released the desktop Haswell-E, which has 8 cores, supports DDR4 memory clocked at 2133 MHz, but the question remains – when will they release the laptop version? With Intel’s tick tock cycle, it shouldn’t be too long before you can get an updated version of the Haswell with the Dell XPS 13.
It should especially be soon, because the next Intel chips (Broadwell at 14nm!) will be released in the first half of 2015.