The CW has never had more than four Arrow-verse shows running at the same time, as Black Lightning is set in a separate superhero universe. It is possible that Batwoman and Arrow will overlap at least a bit, though. Hopefully more details will release sooner rather than later. The possibility of an Arrow spinoff has been floated, and the odds aren't too bad that could happen. If so, the Arrow-verse could come to be comprised of five shows, even without Arrow!