Carnage is Spiderman's mega-villain. He is the ultimate bad guy in spidey's story, and these are a few reasons to NOT bring him out yet.....
1. Venom needs some reconsideration and a revival in the series, the guy who played him,(I don't know his name and I don't even care to look it up.) was a horrible choice for the role, and Marvel needs to find a more masculin actor to really bring out Eddie Brock, and give him at least a whole movie to redeem that character, and remember, Eddie does become some sort of a good guy before Carnage appears.
2. Carnage needs to be the central villain in the movie.
Bringing Venom out towards the end of Spiderman 3 was just awful, but blame that on the hounding of people wanting to see him so badly and the studio had to make a quick decision, so we all got disappointed. With that said, let the series breath with some other bad guys. You got the vulture, the lizard, morbius(who i think deserves the spot light in spiderman 4!), electro, You could make a case for any one them really, well, except for shocker. He could be the opening scene villain.
3. The events of carnage should be led up 2 by the preceding movie, or "The empire strikes back" take.
It would just be cooler that way, and it supports my theory on letting another villain get the spotlight, sides, why do u think the avengers movie is looking so cool?? they are setting it up little by little,or look at it like this, would u rather see a movie that has 2 cram in a whole lot of story in a short period of time, or an after the credits ending were in shows a red symbiote creeping up on an unexpecting murderer??(wen u think about it u can almost picture it!!) That would give us hype about it coming out.
4. When the movie comes out it should be called Maximum Carnage.
That's the name of the event for those who don't know, and if everthing goes to the way I hope it gives it a higher meaning than just Spiderman whatever.