Kaby Lake-X Core i7-7740X and Core i5-7640X were designed for the enthusiast market and they had a rather stonking overclocking performance. However it appears the chips suffered poor sales and there was no point carrying them on.

Some of that was to do with the fact the Kaby Lake-X lineup was outshone by the Skylake-X processors because they offered fewer PCIe lanes, ‘only’ four cores and support for just dual channel memory.

Intel is moving to the X399 platform and will not support four quad core processors with HEDT.

Intel states that  PC makers and component resellers will need to order the processors by November 30, 2018, with the final shipment of Kaby Lake-X chips pencilled in for May 31, 2019. They will be around for another year if you want one.