For a historian, Mein Kampf is a primary source for the events leading up to the Nazi takeover of Germany and subsequent events. A critical examination of the text and the author's inspirations is certainly appropriate, but unless there is something hidden in European copyright law that I'm unaware of, or there are witnesses that are about to die, I don't see any real necessity to do it before the copyright expires. Doing an annotated copy of Mein Kampf no more makes the core text protected from subsequent emendation and interpretation than does an annotated copy of the Bible (much as the comparison makes me gag).