Thanks to 'Minifigure' in a comment on an earlier post for a link to The Brick Life, which is also gathering news on the new theme. So far they seem to have the same news I've found, but I'll watch that space for anything new.
One thing that is unclear to me - The Brick Life site says that the Marvel line is "restricted" to Spider-Man, the X-Men and the Avengers, which implies that they cannot do anything else. But the official press release says that the line will "spotlight three Marvel franchises", which implies to me that they will start with those, but could focus on other characters as well. Of course, I'm not sure how much of a restriction it would be, since pretty much every character in the Marvel universe has shown up in one of those comic lines over the years. Heck, it seems like almost every Marvel hero has been a member of the Avengers at one point or another. I do hope they eventually include fan favorites like the Fantastic Four and Dr. Doom (okay, Doomie has fought everyone over time, but he's usually associated with the FF in my head), also the Silver Surfer is an obvious fig (esp since about every other run of Collectible Minifigures seems to have some sort of surfer).