What Adam was talking about was changes that Hasbro has made to upcoming case assortments.
There were two upcoming cases that were supposed to contain the 501st Trooper - Wave 3, Revision 2 and Wave 4, Revision 2. But, the ratio changed for both those cases and now neither case is scheduled to contain a 501st trooper (replaced by an R2-D2 and Destroyer Droid, respectively).
So, that means that after the Wave 2 cases ship (with the #65 sculpt 501st), there will not be a 501st slotted in a case until at least Wave 5, which isn't due until Nov/Dec. It's easy to see how Nov/Dec could slip to "next year", especially if Hasbro adjusts those cases as well...