According to reports, Samsung has already started mass-producing the Galaxy Z Fold4. Rumoured to be launching this autumn, the Galaxy Z Fold4 is also now thought to contain an improved Under Panel Camera (UPC), along with a narrower hinge design than the Galaxy Z Fold3 has.
https://www.notebookcheck.net/Samsung-Galaxy-Z-Fold4-UDC-improvements-and-design-changes-highlighted-as-next-generation-foldable-enters-mass-production.624212.0.html