The latest TVGuide Megabuzz article included new hints of Castle's finale spoilers:
While executive producer Andrew W. Marlowe doesn't rule out a return from Sen. Bracken this season, he says that character doesn't really figure into the finale. Instead, expect an "emotional" season-ender that pays off some of Beckett's season-long questions about her man. "We've spent four and a half years really unpeeling who Beckett is, but we haven't learned a lot about Castle," Marlowe says. "We want to have Beckett look at that and wonder what kind of relationship she's going to be in if he is withholding stuff. To what extent can he open up and be secure enough with her?" But before you start thinking breakup, let Stana Katic calm your fears. "There are some mini bumps," she says," but there is some high-stakes stuff that brings them even closer."
While TVGuide talks about season finale, TVLine discusses Lanie/Esposito relationship and upcoming 100th episode:
At minimum, they’ll get some sexy-loooking-time. Tamala Jones confirms that, as hinted in the Valentine’s Day episode, the 12th precinct’s M.E. and detective “are seeing each other, and have been secretly seeing each other.” Moving forward, she teased, “I think possibly you’ll see a little bit more action between them. Everybody’s going to be looking spectacular, I can tell you that.”