You've already heard that Joss Whedon was directing Avengers 2 and creating a new Marvel TV series, set in the Avengers universe. So the announcement, a while later, that Whedon had actually signed an exclusive three-year contract to work for Marvel seemed like a minor detail. Except for one thing.
The three year contract, according to Marvel, means that Whedon will "contribute creatively to the next phase of Marvel's Cinematic Universe." You can assume that means Whedon will be involved, at some level, in the scriptwriting of the movies between now and Avengers 2 — especially the second Captain America film and Guardians of the Galaxy.
But then again, you'd have expected Whedon to do that in any case, since he already rewrote the script of the first Captain America and filmed the post-credits scene in Thor. As soon as Whedon was confirmed as director of Avengers 2, it was likely that he'd be having a hand in the films that set that film up. (And Guardians of the Galaxy, as Marvel's most "cosmic" film to date, is widely assumed to be directly tied in to the Thanos storyline that will conclude in Avengers 2.)
What's interesting, though, is the notion that Whedon is contributing to "the next phase" of Marvel's cinematic development — which could mean stuff that comes after Avengers 2, as well as the stuff that leads up to it. Just as Avengers set up the Thanos arc which everybody's expecting to play out in Guardians and Avengers 2, it seems logical that Avengers 2 will set up whatever comes afterwards.
(And this might be a good time to mention all of those rumors that Marvel has been pushing Fox to return the rights to Galactus, a villain who's pretty much unmatched in his power and scare value, in return for some concessions on the Daredevil movie. Could this be because Whedon and Marvel President Kevin Feige want to use Galactus in Avengers 3? After all, how else are you going to raise the stakes after Thanos? The Annihilation Wave could also work, but might be too complicated a story to capture on film.)
Knowing Whedon, and his penchant for sneaky plotting, it seems likely that the "next phase" of Marvel's movies could actually be something that's set up through little hints in this as-yet-undefined TV series. After all, the merest hint that watching Whedon's new TV show is the best way to get some clues as to what's happening in Avengers 2 and beyond could help drive some less committed Whedonites to tune in — although any such hints would have to be subtle enough not to turn off casual watchers.
The main takeaway from Marvel's announcement, though, is the notion that Whedon is joining a very small group of people who make the big decisions about the direction of the shared universe that includes Marvel's movies and this new TV show. This comes at a crucial phase, when most of Marvel's films are going to be sequels rather than origin stories, and at least half those films (Thor 2 and Guardians) are likely to be insanely "cosmic," with the obvious risk of falling into the Green Lantern trap of excessive CG and flat characters.
So most of all, Marvel's on-screen universe is going to have to stay grounded, something that Whedon excels at because he understands that the best stories are "about us."
And here's another possibly-on-crack prediction about Whedon's TV show — it'll be a chance to explore the nooks and crannies of the universe in a way the movies just can't. Whoever Whedon's heroes end up being, they'll probably be able to spend more time poking into dark corners and finding out if S.H.I.E.L.D. uniforms chafe and stuff. I'm sort of hoping for the television answer to Kurt Busiek's Astro City and Marvels — a ground-level look at a superhero universe, where mostly relatable minor characters stumble around away from the huge cosmic battles. (But they still interact with the big stuff somehow.)
(MTV has a few obvious possibilities for what Whedon's show could be: a live-action Hulk show, Alias Jessica Jones, a S.H.I.E.L.D. show, a Secret Avengers show, or Brian K. Vaughn's Runaways. But I would not be at all surprised if the show was mostly a brand new set of characters, not based on any particular comic, living on the outskirts of the Marvel Universe. Or Damage Control, maybe.)
With Whedon on board, Marvel will probably have an easier time planning beyond Avengers 2 farther in advance, and also keeping the underpinnings of its movie and TV universe more solid and connected to bedrock. At least, there's a lot of reason for optimism. Excelsior, and all that.