According to a report, Samsung's engineers are busy addressing Wear OS 3.0 bugs that could hold back the Galaxy Watch 4 and, by extension, the Galaxy Watch Active 4. Renders of the Galaxy Watch Active 4 have leaked too, confirming the smartwatch's design and changes compared to the Galaxy Watch Active 2.
https://www.notebookcheck.net/Samsung-Galaxy-Watch-Active-4-leaked-renders-confirm-subtle-redesign-but-engineers-have-their-work-cut-out-with-resolving-Wear-OS-3-0-bugs.547206.0.html