Christer Bergström's new publisher for the Black Cross Red Star series is Vaktel Förlag of Sweden. Publication date for volume 4 has been pushed back a couple of times and I really hope to see this by May / June 2019.
https://vaktelforlag.se/produkt/blac...ban-1942-1943/
They also have a fb page.
Bergström states that once Vol. 4 is out Vaktel Förlag will next publish "heavily updated" editions of volumes 1, 2 & 3.
http://www.bergstrombooks.elknet.pl/bc-rs/