There will be no SQL 2019 exams.
Microsoft are moving away from "product" focused exams to "role" focused exams and are all based on the Azure platform.
After 70-761/70-762 70-764/70-765 70-767/70-768 are retired, the next path would be the DP exams.
DP-100 (generally available)
DP-200&DP-201 (generally available)
DP-300 (this is currently in beta)
There are other DP exams out their for specific technologies like DP-060, but if you want to follow the "traditional" path then 764/765 will be replaced with DP-300 for the "DBA" role.