April 29th. This forum usually gets a heads up before it goes completely public.
The RSD releases aren't part of any sub. Sub 3 people get to order them separately but that won't apply to sub 4 which is the new one (you would get to order whatever non sub releases did happen during sub 4 though). I would imagine at least some of the RSD titles may appear on the DW site at some point after RSD.
146 sub 4s left at the time of writing btw.