Marc Webb, the director of The Amazing Spider-Man 2, told Collider in an interview that he's not certain whether Divergent star Shailene Woodley will ultimately return as Mary Jane Watson when the character does show up later in the series, after her part was cut by the upcoming film.
"I don't know, she has a lot on her plate. We haven't really crossed that bridge yet," Webb said when asked whether the actress could return to play the role in The Amazing Spider-Man 3.
(Note that the phrasing of his answer suggests that it's still planned for MJ to show up in the third film, if you read between the lines.)
Woodley's part was filmed but then cut from the movie, and when a fourth film was added, it became unclear whether the actress's busy schedule would still allow for her to appear in the superhero franchise.
Early reports were that she had been replaced already, but filmmakers and the actress rumored to be replacing Woodley have all denied that there's any truth to that.
The Amazing Spider-Man 2 is due in theaters in May of 2014, with sequels planned for 2016 and 2018. Rumor has it that by the time the fourth movie is made, the villains will unite as The Sinister Six.