So to start with the easy point; Superhero Comics need more diversity. Note not comics in general, because there is a lot of diversity away from capes'n'tights, and it's important to remember that Marvel and DC are not all comics. But the superhero genre is dominated by legacy characters, mostly decades old, and sell to a predominately white, male audience who have grown up with white, male heroes. Bruce Wayne is a white guy, so is Steve Rogers and Hal Jordon and Scott Summers and....you get the picture. The vast majority date from a time when you would struggle to sell a comic with a non-white face on the cover, but there really isn't any excuse for that now, other than the years and years of brand recognition, right?
Well not really. If we flip to the movies for a minute, Iron Man was hardly an A-lister until Marvel had to root around characters they still owned to make a movie for. With most of their "big" properties with other studios they had to drive him into a public consciousness where the passing cinema goer probably wasn't really aware of him. If you think about it, Marvels big female hitters are also "lost" to them with the X-Franchises, Fantastic Four and so on, and the success of Black Widow as a character proves more than anything else you can "grow" awareness from a minimal start. I'm not sure Falcon would be taking on Captain America's Shield if he hadn't been so successful in The Winter Soldier, either.
Back to comics, Marvel are clearly positioning themselves as a diverse company with a wide roster of comics aimed at non-traditional fans. I don't think we should be under any illusions as to why, either; superhero comics is a business, and you make money in this industry by keeping old audiences buying and bringing new audiences in the door. And new audiences are going want to see characters they can relate to, just as the old audiences do, and a younger, more diverse audience is going to want a more diverse set of characters to read. Hell, I'm an old, non-diverse audience and I'm bored as hell of recycled white-guy superhero storylines.
But the problem here is that it takes time to grow new characters, and in the cutthroat world of comic shops, the shelf space goes to the big sellers, being sold to the old hands. So if you want to make a point, shaking up a few of your main titles makes a lot of sense; it gets a lot of publicity for free, it has an established audience already, its actually a fairly low risk change. After all, Thor has been a Space-Horse and a Frog, so its not like the its the first time he's not been a white dude. This somewhat cynical analysis shouldn't preclude welcoming the move - although I'd be the first to recommend looking at the excellent Captain Marvel or Black Widow comics for more permanent (probably) female-led comics.
Now, over at DC they seem to have spent the last few years addressing concerns over falling readership by focusing on shoring up their base. There has been something about the New 52 that really never appealed to be, a focus on "serious" and "edgy" combined with what felt like, from the outside, a belief that every comic should in some way be Batman. You're never going to get much movement on the diversity front, or even the "strikingly original story" front that way, and my worry is that seems to cross over to the movies as well. In theory, DC/Warner should have a coherent, top-to-bottom strategy, and the huge advantage of controlling all their properties, but they've floundered; Man of Steel was Superman for the Batman fans out there, and Dawn of Justice may herald a brighter future but it radiates more of the same brooding tone when Marvel seem to be swimming in cash from good old-fashioned upbeat crowd-pleasing.
Neither studio, however, seems to want to take a punt on a non-white-dude lead character yet, which is a shame. I think - and its more a gut feeling than anything - that Marvel are ahead on this front, largely because they seem to do a better job with the supporting cast across their franchises. Its hardly a glowing "well done" star of course, but it's important to recognize progress when you see it, rather than just stand at the sidelines yelling "perfection now!".
To try and wrap this ramble up, I guess I'm saying that I'll take progress where I can get it. A few bits of admittedly trick-casting isn't going to make the superhero comics scene a better place - especially if its not reflected in creative talent as well - but its a sign of shift in the mainstream that is welcome. And lets not forget that diversity isn't just about getting a few more women or characters of colour; its about sexuality, disability, age, culture and everything else. It's about being diverse. I don't want superheroes that cater to the same people that they've always done, I don't want to see the genre treated as a vast clique that fears change and outsiders. I like superhero comics, and I want them to be better, and broader.