Isn’t that the million dollar question, Anon?
I’ve spent the past couple of days thinking about this one, trying to reconcile the happy, wholly in love couple that we saw at the end of season seven with a pair of people who are willingly calling it quits; however temporarily that might be.
The short answer is that I can’t. Not without some life altering, devastating thing that would reduce them to relationship rubble. The death of a child would certainly be one, or some sort of permanent injury that one of them blames the other for (which I admit I’m drawing solely from Grey’s Anatomy when Callie cut off Arizona’s leg to save her life). Maybe if Beckett lost her job due to Castle meddling around, or Castle got dropped from Black Pawn due to something she did there could be enough long term story to grow and foster a break up, but given this is supposed to be happening in early fall (and that means within the first three episodes to me) I don’t see how you get there from season seven’s finale and have it be a mutual thing.
So, what if its not? What if one of them has no choice in the matter? We always talk about how this show is fanfic come to life with these two idiots and their love story. A big fanfic cliche is shoving someone into witness protection or forcing them to disappear over night for the protection of themselves and their loved one. I said yesterday that we needed a new multi-episode villain to enter the fray, and given that the season premiere is the first chance Hawley and Winter have to show us their version of Castle, why not start with the big guns?
So here’s my current working theory: if the blind item is Castle, their “break up” is because one of them has to leave to protect the other. There’s no opportunity to face it jointly, there’s no chance to come together and agree that the whole family goes and deals with it. One of them drops out of sight, maybe even stages some dramatic break up fight to give the disappearance credence, and then temporarily goes into hiding. That’s a break up that will change the DNA of the show, but not something that is going to last forever nor derail the show for good. But it WILL piss people off and polarize the fandom regarding the motivations behind the choice.