Predicting the timing, outcome and authorship of Supreme Court opinions is a notoriously inexact art (I would not dare call it science), but with as much of an educated guess as one could muster, SCOTUSBlog believes that the Court will wrap up its term by next Thursday (the Court has ten cases left on its docket) and that the lead opinion in the Heller vs. DC Second Amendment/gun control case will likely be written by Justice Scalia (although Justice Souter is the other main possibility, and the SCOTUSBlog folks note that the lead opinion may not necessarily command a majority of the Court in a case of this nature). My own best half-educated guess is simply that the Court will probably not hand down Heller on Monday, the next day when opinions are scheduled to be released, but will include it in the last day or two of opinions.
Interesting personal note: Justice Scalia has recounted how in high school he used to carry his rifle to school on the New York City subways. It was a different age, and a different city.