Wild Opinion Speculation
[Corrected at 11:48]
There is very little information that can be gleaned with confidence about the authorship of the remaining opinions from the Term.
It does look exceptionally likely that Justice Scalia is writing the principal opinion for the Court in Heller "“ the D.C. guns case. That is the only opinion remaining from the sitting and he is the only member of the Court not to have written a majority opinion from the sitting. There is no indication that he lost a majority from March. His only dissent from the sitting is for two Justices in Indiana v. Edwards. So, that's a good sign for advocates of a strong individual rights conception of the Second Amendment and a bad sign for D.C.
Backing up to February, there are two remaining cases (both argued, like the guns case, by Walter Dellinger): Morgan-Stanley (an energy regulation case) and Exxon (the maritime punitive damages case). Six Justices haven't written from the sitting, making predictions very dicey. The best guess is that Chief Justice Roberts and Justice Stevens are writing. Justices Scalia, Souter, and Kennedy are unlikely because they had already written twice in a sitting before February. Justice Ginsburg wrote twice in later sittings.
For April, there are four opinions remaining: Plains Commerce (involving Indian tribes), Kennedy (death penalty for child rape), Davis v. FEC (campaign finance), and Giles (a Confrontation Clause case). Justices Scalia, Kennedy, and Alito have not written and therefore almost certainly have three of the opinions. The most likely author for the remaining decision is Justice Souter (who needs another opinion to take him to seven for the Term).
With the exception of Heller, these predictions have no genuine value. They are just informed guesses and none says anything about the outcome of the cases.