Rumours about the third installation for Black Lagoon is spreading like a bushfire throughout the net by now, still unconfirmed and I couldnt find any update for this sensational news. As a Revy fan myself, I was happy when I heard about this and looks like even animenewsnetwork itself has also reserved a slot for this anime HERE.

Quote from myanimelist.net

According to the store window advertisement of the first volume of “Black Lagoon” novel, the production of its third season was announced. The advertisement only tells the decision of the production. The airing schedule is unknown.

For now, we can just wait for the official announcement, who knows what this third season of Black Lagoon will have for their fans out there.