Well I'm not totally sure I agree with that. I guess it depends when rehearsals/filming are actually going to start & also how long a 'tour' through europe Kirsten & Jason are planning.
If it's a short tour (of say two weeks) starting next week coupled with a late march start to filming it's definitely doable.
Having said that I do agree it's unlikely that Kirsten will be in this film now. I' m still baffled as to why it's still being reported that Blake Lively will be playing Glenda though (unless they have either completely rewritten the story for the film or Blake got very mixed up during that interview

).