Back 4 Blood looks set for Xbox Game Pass day one.
Redditor JohnTLH spotted the news in the YouTube description for the upcoming Back 4 Blood PvP video reveal, which is set for 10pm UK time on Sunday 13th June.
That reveal follows Microsoft's E3 press conference, which kicks off at 6pm the same day. I suspect the announcement will be made - officially! - during Microsoft's press conference.