According to reports from China, Apple will start mass-producing its next iPad Pros between the end of this year and the start of 2020. The upcoming tablets will be manufactured in Taiwan before a spring or summer 2020 release.
https://www.notebookcheck.net/Next-iPad-Pros-to-enter-mass-production-in-Q4-2019-or-Q1-2020-New-report.419657.0.html