Leaked slides have revealed that Intel's 9th generation 'Coffee Lake-S Refresh' CPUs such as the Core i9-9900K will be available from Q1 2019. This comes as a surprise as we've been expecting a September 2018 launch so far. The slides also indicate that new 'Cascade Lake X' CPUs will debut by Q4 2018 as anticipated.
https://www.notebookcheck.net/Leaked-slides-point-to-arrival-of-Intel-Core-i9-9900K-in-Q1-2019-Basin-Falls-Refresh-Cascade-Lake-X-to-debut-in-Q4-2019.320114.0.html