SCOTUSBlog, of course, gets the jump on the first analysis of Heller v. DC, striking down the gun ban, noting:

Second, what standard of review will apply [to future cases]? Scalia rejects rational basis (note 27 page 56, which the District did not urge) and says that the District law falls under any other standard, without exactly saying why. The SG offered a fairly relaxed standard (except as applied to the DC law), but the Court did not bite. Federal laws regulating guns, and perhaps those increasing sentences for gun use, are likely to be challenged, whatever the standard and chance of success.

Here’s the note:

27 JUSTICE BREYER correctly notes that this law, like almost all laws, would pass rational-basis scrutiny. Post, at 8. But rational-basis scrutiny is a mode of analysis we have used when evaluating laws under constitutional commands that are themselves prohibitions on irrational laws. See, e.g., Engquist v. Oregon Dept. of Agriculture, 553 U. S. ___, ___ (2008) (slip op., at 9–10). In those cases, “rational basis” is not just the standard of scrutiny, but the very substance of the constitutional guarantee. Obviously, the same test could not be used to evaluate the extent to which a legislature may regulate a specific, enumerated right, be it the freedom of speech, the guarantee against double jeopardy, the right to counsel, or the right to keep and bear arms. See United States v. Carolene Products Co., 304 U. S. 144, 152, n. 4 (1938) (“There may be narrower scope for operation of the presumption
of constitutionality [i.e., narrower than that provided by rational-basis review] when legislation appears on its face to be within a specific prohibition of the Constitution, such as those of the first ten amendments. . .”). If all that was required to overcome the right to keep and bear arms was a rational basis, the Second Amendment would
be redundant with the separate constitutional prohibitions on irrational laws, and  would have no effect.

That’s awfully circular — the right to equal protection under the laws is obviously a "specific, enumerated right," but it is well-settled that there are numerous classes of discrimination that get different standards of review. For example, discrimination based on race is reviewed strictly, discrimination based on sexual orientation is reviewed for rational basis, while discrimination based on gender is reviewed on an intermediate standard.

Same goes for the "specific, enumerated right" of free speech — limitations on indecent speech are reviewed differently from political arguments.

it sounds like the Supreme Court could not get a majority to agree on a standard, so they dodged the question entirely. Sometimes that is understandable, but not here, where they are completely overhauling the interpretation of a constitutional amendment.

My bet is that this case goes the way of the failed Commerce Clause cases of the 1990s: a sweeping constitutional protection that disappears when the absence of popular support is revealed. There will be new challenges to gun laws, but not a complete repeal of the existing system.