Sorry for reviving an old thread, but I haven't found a final conclusion
anywhere.
I've run into this problem[1] with a Seam 3 sample application. Besides
Seam 3, there are other (even JBoss) projects (Seam 2, perhaps
RichFaces, etc..) which have sample applications that rely on DefaultDS.
It is not likely for these projects to adapt to this change and have a
release before the AS 7 is released. Therefore, I think we should
maintain backwards compatibility as much as possible so that (most of)
the sample applications working on JBoss AS 6 can be used on AS7 out of
the box.
[1]
https://issues.jboss.org/browse/AS7-975