In 2010, just make the numbers start with "31".
IE: AD3101, CAD3102CD, JAD3103CD, HAD3104CD, GAD3105CD, AD3106, etc...
This will handle the next decade handily. Then, in 2020, go with a
"41" prefix, IE: MAD4101CD, etc...
As Jo mentioned, numbers don't really mean anything anymore so the
above scheme will fit in well at the "new" 4AD.
I found this:
http://i41.tinypic.com/5fn9dc.jpg
Note that it is indeed a CAD, not a DAD.
I'm interested in hearing more from new artist Ben Gizzard too.