"400,000 clergy and laity"
Maybe worldwide, but that number seems a bit inflated to me. The TAC is not a large group in the US, but does have a larger number of members in Africa and the Far East.
Also there have already been parishes leave the TAC over this and others are watching and waiting to see what happens, so I think the numbers will not be what anyone is anticipating if this comes about.
How do I know this? I'm a member.
OTOH, there are some of us ex-Episcopalians who woudl be very happy to join a local TAC parish should it suddenly be in Communion with Rome.