If I knew the official announcement of Sam Wilson (the Falcon) picking up the mantle from an aged Steve Rogers was coming so soon, I would have waited to write my post on the new Thor, since many of the points I have to make are the same. But here I'll focus on the aspects unique to Cap.
1. Ever since this was hinted several weeks back, I've thought about it in terms of two issues: who becomes the new Cap, and why are they replacing Steve Rogers at all. The first is a no-brainer, and personally I'm thrilled to see Sam as the next person to wield the shield. I think this a win all around: it flows naturally from the story Rick Remender has been telling, and Sam is the natural successor to Steve (given that Bucky already had a shot), having been his crime-fighting partner and close confidante for years. Furthermore, it helps to diversify the Marvel line in the same way that the female Thor does, which I only hope will be justified and motivated in-story as well as Sam's ascension is. (The same issues with legacy that I expressed in my Thor post hold, even though there have been almost as many different Caps as Thor has had helmets.)
2. The bigger issue for me is: why is Steve Rogers being replaced again so soon after he came back from "the dead" several years ago? (It seems like yesterday, but possibly that's because I have no life.) There are a number of possible reasons.
First, it may have been motivated for the express purpose of putting Sam in the red-white-and-blues. Nothing wrong with that, though it does seem to make Steve Rogers disposable and imply that Sam Wilson can't be made a more prominent fixture in the Marvel Universe as the Falcon—which, after all, is an original, nonderivative superhero identity without "Black" in the name, and something I think should be celebrated.
Second, it may be part of a larger character arc for Steve Rogers—in much the same way that Rhodey first served as Iron Man during Tony Stark's fall and rise from the depths of alcoholism, only to have Tony reclaim the armor when he was all better—but this would diminish Sam's stature as a "true" successor as Captain America and make him little more than a placeholder. He would get his moment in the sun, true, but he deserves better.
Third, it may simply be a "hail mary" on the part of the creators. I've found Remender's run to be less than inspiring after an impressive start, and this may have been the best Cap story they could come up with. If I remember correctly, Cap has been "depowered" twice since he was reborn, and that well has run dry—which leads me to think this was motivated by one or both of the reasons above (or simply a desire to mix things up, as I'll discuss below).
3. Let's abstract away from the new Cap and talk about Marvel in general. In my post on the new Thor I expressed my suspicions that all of these abrupt changes in major characters were leading to a Marvel reboot down the road. Maybe it's not, and many if not all of these changes will be reversed in a year or so. Regardless of how long these changes stay in place, however, and no matter how much I support each of these changes individually and look forward to the stories that can be told with them, taken together they reek of the same desperation that led DC to reboot their universe three years ago: short term shock to goose sales. As Brevoort says in the interview announcing the New Cap, “Change is one of the watchwords of the Marvel Universe, so there are even more startling surprises to come!” This sounds to me like "change for the sake of change," which I regard as a shortsighted alternative to solid, innovative storytelling rooted in the rich history of beloved characters.
But I'm not running Marvel Comics, and I'm no expert on what sells comics to the majority of current fans (or the elusive "new fans" they hope to elicit). Maybe current readers want rapid change that keeps them on the toes. Maybe they don't have the same appreciation of decades of continuity and character development that we old fogeys have. DC certainly seems to have banked on that, and even though their editorial and PR problems of late are well documented, few of them seem to deal directly with lost continuity. As long as Marvel avoids a total reboot, they will retain that history that many fans love, and will also be adopting a concept of legacy similar to what DC had before the New 52 (as I discussed in the last post). This may be inconsistent with the appreciation many longtime fans have for the characters, but may appeal more to new ones. (I don't know.)
Again, I sincerely hope I'm wrong. After all, look at the Superior Spider-Man, which exceeded almost everyone's expectations in terms of storytelling, after which (to me, at least) Peter Parker as Spider-Man once again seems almost blasé. Fantastic stories were told of Bucky Barnes when he served as Captain America, and I hope the stories of Sam Wilson as Captain America (and the new Thor) will be just as good. At the end of the day, there are two things that matter to me: story and character. If good stories are told that respect the characters and develop them organically, I'll be the happiest fan knocking down the door of my local comics shop every Wednesday morning. But with Marvel right now (or "Right NOW!"), it just seems like too much all at once, and that worries me.