I don't believe DTA referenced "new" cases in any way, and as far as the intent of Congress, you know that the conservative jurists really won't care (as a strict constructionist, if DTA doesn't say "new cases" then it doesn't mean "new cases"). This is where Alito and Scalia would likely bump heads (though probably coming to the same conclusion regarding the meaning of statute): Alito is much more likely to use legislative history (and the perceived intention of Congress) than Scalia (see this terms U.S. v. Zedner in which the two duke it out over this idea).
Not explicitly, no. Section 1005(h)(2) states "REVIEW OF COMBATANT STATUS TRIBUNAL AND MILITARY COMMISSION DECISIONS- Paragraphs (2) and (3) of subsection (e) shall apply with respect to any claim whose review is governed by one of such paragraphs and that is pending on or after the date of the enactment of this Act.". The paragraphs it is referring to hear are the ones that limit the Court's jurisdiction over these cases. Basically, the Act is saying that any claim for reviewing combatant status (which is at the heart of any habeus corpus request or demands for PoW/Geneva rights) after the Act is passed can not be heard by the Court, hence my saying no new cases. The Court in this case, however, judged Hamdan to be pending before
the Act was passed. Therefore, it had jurisdiction and therefore it could rule against the military tribunals and, I'm sure by no coincidence, against DTA restriction of judicial power.