Looking forward to the movie, for two reasons:
1. Nagisa animated!
2. Good way to attract attention to my translation project!
TOEI can either do this two ways; they can either, as Sushi-Y said, have a barebones version of Nagisa's route (would that cover both School and After stories?). Or, they could do a completely original scenario that only involves Nagisa and ties the 幻想世界 a lot more than it should be. Maybe to the point where it's more like the AIR movie was. Not saying it's bad, I haven't seen it myself, but you never know when you only have 90 minutes.