The official Twitter account for Shogakukan’s Monthly Sunday GX magazine has announced that Rei Hiroe will resume the Black Lagoon manga in the magazine in September 2019, with “more surprises planned.”
Black Lagoon was initially announced to resume in Spring 2019. The manga had resumed in May 2017 following a hiatus that began in early 2014, but then went on hiatus again in August 2018.
Hiroe launched the Black Lagoon manga in Monthly Sunday GX in 2002. VIZ Media publishes the manga in English.