Once upon a time, you went to the newsstand to pick up the newspaper, some highbrow and lowbrow magazines, and the favorite comic books. That was the first comic book distribution system. It was marked by a wide variety of genres and publishers until about the 1960s.
Then comic book stores and the direct market sprung up. That was the second system, and it was marked by the dominance of superheroes, DC and Marvel superheroes especially.
Now DC and Marvel are making considerable gobs of money outside comic books while Diamond's anti-small-publisher practices portend a potential mass move to the Internet and comics are starting to bang on the door of bookstores.
So if DC and Marvel eventually decide to scale back and rethink the way they do comic books, Sean Kleefeld thinks that will be the death of Diamond.
I'm not sure what will replace it or if anything other than webcomics replaces it, or what the third system will look like, either in terms of the distribution mechanism, the selection of genres, or the diversity of publishers. But it'll be very different from the second system.
(The model of the monthly comic is really rooted in the first system. If DC and Marvel decide to move to mostly a graphic novel format, or move entirely to the web, I think you'll see those "pamphlets" become basically unheard of.)