2600K doesn't have a direct replacement, whereas the 2700K does.
small typo
Even though there is no increase in the clock speeds, that is not the only selling point. They are expected to have a (small) performance boost at the same frequencies, but the main selling point is the reduced TDP, improved integrated graphics (150% to 200% improvement in graphics benchmarks, for anyone that relies on the integrated graphics). The reduced power consumption and reduction to 22nm technology have also allowed Intel to give a higher maximum multiplier, giving overclockers a chance of even greater performance benefits.
Not a major selling point if you already have a 2600K or 2700K, but great for new buyers that can wait that long