https://www.bungie.net/en/News/Article/46085
Set things to transfer to a D2 clan -- looks like the change happens on August 23. Anyone who is only part of the group and not a member of the clan will be removed (guessing this means the people who joined the group but didn't designate it as their clan).
We currently have 130 group members and 77 clan members. If you want to be part of the BG clan in D2, I'd recommend checking to make sure you're part of the clan to be safe. If we hit 100 clan members, I'll go through and start looking for people to kick based on last play-time -- might need to eventually create a second BG clan and set up an alliance, although they haven't detailed anything about allegiances yet..