[Snowflakian]

Antman is part of it, his movie isn't coming till after Avengers though.

I'm hoping they didn't go the loki route, because we'll get enough of him in the Thor movie, and thor vs.

Norton is also in control of the hulk now, or at least alluded to at the end of his movie.
Norton is already signed on, as is downey. It was in the contracts for their first movies. The 'avengers clause'. Caps and thor's movie have it too.

From what I've heard they may completely skip over the fighting the hulk aspects. As it's been done in hulk vs. and the ultimate movies. But I do hope the first half of the film does have some hulk fighting the avengers, and I'm hoping the second half is either Ultron, or something of similiar oomph. Ultron honestly should probably wait till the ant-man movie, but ah well.

Hulk's movie attempted to tease about his avengers fight by having the weapon 0 formula in use. So that would be sweet to see, but I don't think Loki is a big enough bad for this new team. Leave that for the Thor sequel. Since his movie from last report was mostly on asgard, with a lil midgard at the end.

Now let's also keep in mind, they tend to approach these in manners that haven't been done before. This being said, I'm hoping this means the kree/skrull war won't be till later, which could add Ms. Marvel to the cast. Movie Ultron could be interesting, but we need ant-man as the intro way, though that could be the entry-way into the ant-man movie.
That also leaves, Kang, the Masters of Evil, the Zodiac, Immortus, and more too though.

Now I could see them maybe doing the hulk at the start, followed by the masters of evil later, with the leader being revealed as loki all along. But honestly, I'm hoping for big bads that are new to this universe entirely, as opposed to carry-overs from other movies.
I could see maybe some carry-over, like ultron taking over the remains of Iron monger, but loki himself is too much thor imho for one movie. We need a well balanced epic battle. Though then again, loki is like the ultimate reason why ultron etc would go bad.

I'm just really curious to see what direction this goes.
But yes, all the new marvel films since hulk that aren't fox or new line, or sony, have something called 'the avengers clause' so all the main hero stars will be in avengers.
The side stars don't have that clause as was the case with samuel L jackson getting resigned for the next 5-6 films. We may see this again when war machine comes into play, among other cameo guys from the films. I'm also unaware if loki has that in his contract. I do know thor did.