***Essentially, it did not address the registration issue....***
Presuming I grant your reading, it is a slippery slope and one that will be hard to climb. Liberals are professional cheats. Give them an inch and they will take a mile.
My reading is that Scalia went out of his way to point out that Heller didn't challenge the registration requirement; in other words, he explicitly put in the opinion that the question was not germane to the case at hand.
Several of his comments toward the end of the opinion seem to be laying out a "road map" of what challenges should be made to expand upon the Heller decision (the limits of "reasonable" regulation, the incorporation issue, and the issue of registration requirements).