The mythology of Spider-Man has been more or less solidified after nearly 50 years of comic books, movies and television programs. As such, there are certain components that are going to creep into any adaptation of the character and his adventures.
For instance, the radioactive spider bite, the death of Uncle Ben and the nerdy nature of Peter Parker are central elements of any Spider-Man story. Marc Webb's The Amazing Spider-Man hit all of these points, but he added enough of his own ideas about the web-slinger so that his picture would stand apart from the Sam Raimi franchise.
However, The Amazing Spider-Man 2 will begin filming in February, so the Spider-Man universe has to expand. That means adding two central characters -- Mary Jane Watson and Harry Osborn.
Mary Jane was played by Kirsten Dunst in the first series, and while she wasn't his first romantic interest in the comics, she was basically the love of Peter Parker's life. What her role in the sequel will be is unclear, but she will be played by Shailene Woodley.
James Franco played Harry Osborn the last time around, giving a great performance as both friend and competitor to Peter. His role has yet to be filled, but /Film indicates that the competition has narrowed to three men. Alden Ehrenreich of Beautiful Creatures, Brady Corbet of Melancholia and Dane DeHaan of Chronicle are apparently at the top of the list.
What this means for the franchise is unclear. After all, both Harry's father Norman and Harry himself have worn the mantle of the Green Goblin, meaning that the villain could make an appearance in this or other installments.