Brad McKay in the Toronto Star writes about the downturn in the comic book market, and postulates that the lack of diversity, and in particular, a failure to embrace the African-American market may be responsible.
On some level, the downturn in the comic book market is a perpetual story. A decade or so ago, the end of the collectibles bubble market nearly killed the industry (at least, if you tend to believe the headlines). I don't want to make it sound like I disagree with McKay's point, which is that comic books are amazingly homogeneous—white, muscular men, and busty white women in skintight outfits rule the day—but comic books are far more than just superhero comics, and comics other than Marvel and DC are having a heyday both artistically and in the marketplace. Just check out the manga section of your local bookstore—really, I dare you—or check out the increasingly well-reviewed and available graphic novels which are the artistic progeny of Art Spiegelman's Maus.
The only comics that are hurting are superhero comics, and the only place that they're really hurting is on the newsstand. (Collected and bound volumes of serialized superhero comics sold in bookstores as "graphic novels" are matching if not surpassing newsstand or direct market sales of individual issues.) It may well be that superhero comics will be written and sold only as longer, bookstore-friendly volumes as opposed to the traditional 32-page newsprint once-a-month issues. (Which are also no longer printed on newsprint and are, accordingly, rather expensive—another issue that no one seems to talk about.)
Ultimately, comics will survive, although the comic book stores I remember hanging out in as a (rather geeky) teenager are already largely gone. If direct market serialized comic books are to survive, I think that they will have to undergo the genuine rebirth that Marvel's "Ultimate" imprint only hints at.
The real problem facing comic books (other than hackneyed writing, which has always been a problem) is that the most famous and popular characters are between forty and sixty years old. When Captain America was born, he was a soldier in WWII, immediate and relevant. Likewise, the Fantastic Four was a 1960s dysfunctional family unit, and Spider-Man was a geeky teen. If comics are to recapture the youth direct market, they will have to be cheap, well-written, and capture some part, either banal or mythological, of what it is to be a child growing up in the world today.
That's what the superhero comics of the golden and silver ages did, and that's (not coincidentally) what manga is doing now.