June 10th is when volume 5 starts up (Speculation)
It might be the final chapter too (For now...).
Binge volume 4 now if you'll need to remind yourself of the plot points would be my advice.
Yes, final season. Trailers, lots more on BBC-A channel:
BBC-A: https://www.youtube.com/watch?v=UxfLQXdkUPw (extended)
Space TV: https://www.youtube.com/watch?v=Lam5u7yyL90