Sony recently announced that a Sinister Six film is to be released in 2015. So does that mean the villains in the Amazing Spider-man sequels all survive?
That's a good question.
Even though this news does imply that the villains from the new movies will survive to appear in their own spin-off, it's worth knowing that there have been several different line-ups for the Sinister Six over the years - see this marvel Wiki page for more details.
It is entirely possible that Sony could introduce a new member should one fall by the wayside, however, considering the recent Hollywood predilection for setting up big ensemble pictures, I wouldn't be surprised in the least to see every baddie survive the three Spider-Man films.
No one really dies in comic books. Least of all villains. They are always defeated, but always return again - either by miraculously surviving, having their name and mantle taken up by a family member of protege, or any other plot twist to return a fan favorite character to the page.
While this tradition isn't as noticeable in superhero movies, mostly because there are far fewer movies than there are comic-book stories, I still think it's the it's a part of the genre: bad guys are defeated, not killed.
Given that particular genre trope, I don't think a film focusing on a group of recurring villains from previous movies can be considered a spoiler. Recurring villains are a part of the genre, not a plot spoiler.