"Every time I've gotten a chance to play with Norman Osborn, he's been under someone else's purview. Either while Warren was doing Thunderbolts, or while Brian was doing Dark Avengers. Someone else had ownership of that character, and because of that, I was limited with what I could do with him. I couldn't do anything that would mess up someone's plans," Slott admitted to Newsarama. "If you're a Spider-Man writer, and Norman Osborn's alive, who wouldn't want to play with the Green Goblin? When Brian last left the character, he was in a coma, which is a great place to leave a character, because any writer can go, 'And then he wakes up.' Not kidding. A coma is a great place to leave a character. It sounds horrible in the real world, but in the world of comics, it's a very polite thing to do. I'm dying to do some Norman Osborn stuff."
The writer added, "There's that feeling of, 'Whoa, we're free and clear on the Norman Osborn side,' but you want to have some space. After Brian does this seminal return of Norman story in Avengers with the Super-Adaptoid twists, you don't want to immediately go, 'And now he's over in Spider-Man, next month.' You want to give it some time to breathe. But I have every intention in the world of using Norman Osborn fiendishly."
Of course, there's been some speculation that Osborn would show up in the final two issues of Amazing Spider-Man to play a role in the currently-ongoing Doctor Octopus story. And regardless of what Slott might say, it's not outside of the realm of believability to bring a character back into action sooner than you wanted if it suits the story. Remember - just a month or so after Kevin Smith "killed" Mysterio in Daredevil, the Spider-Man books were using the character again.