If you want to know because I know many of them:
AZ: Done. He's nowhere to be found. Haven't checked his channel for months.
Sisiutil: Answering newbs' questions and attempted recently to renew with his narrative past
Dhoomstriker: SGOTM, still really active, but only there. I am in the same team as him, but got low on time to deal with SGOTM
Ghpstage: Around answering technical questions (just like I do)
Lymond: Still around everywhere but far less active
Mylene: Got a breakdown and changed username (ask me privately if you want to know the new one)
Most of the list is dead. Sadly, Civ4 is having a huge exodus.