The movie sounds like it might follow the events of the latest yet-to-be-released side story novel where there is a new character "Maho Hiyajo" in "The Pandora Loop of Eternity". Kurisu mentions she can't control her memory and losing the meaning to live in the trailer so, I'm guessing it might be the same story.
Not sure if I'm allowed to say any more than that here but the summary of the novel sounds interesting
Spoiler for Novel summary:
There is an AI named "Amadeus" that contains Kurisu's memory which might be how she decides to store her memory when she loses them.
Meanwhile, Okabe continues his search of the real Kurisu but has no clue as to where she is until someone named "Shiina Kagari" contacts him.
http://www.famitsu.com/news/201211/22024883.html
Or... It will be different and be the same as the game sequel "Phenogram" that's just been announced XD