It's not just abc who decides to release it, marlowe has to decide too. Because for the AU episode of Grey's Anatomy last night, the first ten minutes was also released of it last week, and Shonda Rhimes (the shows creator) had to agree to do it. It's technically up to the creators not abc. And something big happened in Grey's so my assumption is that something major is going to happen in Castle as well. :)

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