They are surely going to play Spidy in.
Mark my words, there'll some events relating the Avengers Initiative in the new Amazing Spiderman movie (just like they did in Iron Man 2, Thor ect..).
There was also talks to make an Ant-Man movie before the Avengers release but they couldn't. It's still on the talks though; perhaps they could make it before Avengers 2 this time. Personally, I'd love to see Ant-Man since he was one of the originators of Avengers. Also, will love to see Wasp. It needs another hot lady; though Scarlett is hot. Needs to double the dose in Avengers 2.
Personally, I love the idea of Avengers movie. It can go to a large number of sequels but also, it can introduce a number of characters here and there. Then they do a movie to detail a character completely before or after the release of an Avenger movie. Like they give depth to their character in a solo-movie and then, just kicks some serious ass in Avengers. I'm sure, many more people are interested to see a Hawk-Eye movie than, they were before The Avengers released.
Right now, there's only Spiderman as new reboot in the Marvel camp and I'm pretty sure, Avengers 2 might come up pretty soon. But, if they keep entertaining with the Avengers series, then we are going to see 2-3 new characters in every new movie. Perhaps, the concept of rebooting the Fantastic Four series and to keep moving the sequels of Wolverine movies will take more significance now.