Probably not all CG shows have douga (especially
the fully rendered ones... though they might still
have paper storyboards *hopes*) but for now, it
seems that most of the digital ink and paint shows
have douga.  I can't say 100% but it seems highly
likely.

As for release for these pieces of artwork, I'm
guessing some haven't shown up due to perceived
lack of interest or because of just general time
lag and other factors.  With cels it seemed that
some were released closer to the air date of the
series while others waited a couple years.  We're
seeing some series douga (RahXephon (and other
paperworks), FMP) and other series layouts and
genga (Chobits, Azumanga) so I have faith
eventually most series will come out.  Of course,
some studios will probably continue to release
less or not release much at all.

I suppose collecting from CG shows is still in
it's infancy so a lot of this is just (my)
speculation.  It seems a little early to say what
'usually' happens.  I would like more information
as well ^_^

Keys
~wouldn't mind some X TV genga... not to mention
others... genga wishlist starting to eat cel wishlist~