Although there is no official confirmation of the date yet, the latest rumors say that Intel will launch the Cascade Lake processors for the LGA 3647 socket next month. The Cascade Lake-X processors for the LGA 2066, on the other hand, are expected to come out in June, at this year's COMPUTEX trade show.
https://www.notebookcheck.net/Intel-Cascade-Lake-LGA-3647-coming-next-month-Cascade-Lake-X-LGA-2066-in-June.413854.0.html