In a product change notification from Intel, Kaby Lake-X series CPUs have been retired to end of life status. The X299 platform processors only launched last summer around the same time as Skylake X models.
When Kaby Lake-X launched, it was already in an odd position. The i7-7740X and i5-7640X did not offer any real performance difference compared to the i7-7700K and i5-7500K, yet their platform cost was significantly higher. Coupling higher power consumption and the fact that Ryzen was attractive to enthusiasts seeking more cores at lower cost, Kaby Lake-X just did not make sense to buy (not for nothing we scored it a low 40 out of 100!).
Officially, Intel will be phasing out the Kaby Lake-X CPUs starting on May 7, 2018. Changes apply to both retail box versions as well as OEM tray packaging. However, orders are still able to be placed, canceled and returned by retailers until November 30, 2018. As far as end users are concerned, lack of further support is unlikely to have an impact.
Considering the overall abysmal value of Kaby Lake-X, it was only a matter of time before this short-lived series met its demise. With rumors of Intel's Z390 and X399 platforms surfacing, now seems to be a good time for Intel to try and leave its past behind.