According to Mikako-shi in her today radio program, she's not aware of the details regarding the End-of- Year event. Plus she has no idea who's coming to the function. The (probable) nail on the coffin is that the voice of Marika said she has only slight idea about the movie and the recording haven't event started.
....Oi!
If possible I would like Utsunomiya Takashi to voice a character in the movie just for shits and giggles. :P