Firstly, just a couple of comments. I was devastated to hear that Stana wouldn't be coming back if there was a S9 - I think it's pretty obvious that Beckett is my favourite character in the show, but also I cannot see how the show would work without her. Yes, it's called 'Castle', and he is the titular character, but it's never been just about him. The two episodes in the whole show where Beckett didn't feature just felt empty, like something (or someone) was missing, and I dreaded to think what a whole S9 would be like without Stana.
I also dreaded how they would write Beckett out. The most obvious plot I could think of was she would be killed off which a) is pretty lazy writing, and b) I would probably cry for a week. Also, I've been there and done that with Robin Hood and Spooks and Ashes to Ashes, and I really hoped that I could find just ONE fandom where my ship ended in happiness and/or the lead female character wasn't killed off for the purpose of the male character's angst.
The other potential plot I thought might happen was that Beckett would be put in witness-protection or something, without Castle, so she might be mentioned in S9 but never actually seen. IMO, also a less-than-desirable outcome for my favourite character.
So, when I heard that Castle was being cancelled completely, and therefore there wouldn't be a Beckett-less S9, I was actually relieved. Despite avoiding spoilers, in articles that said Castle was being cancelled, mention was made of an alternative contingency ending that had been made in case the show was cancelled. My worry was that both Beckett AND Castle would be a) killed off, or b) put in witness-protection together.
And so, onto thoughts about the actual ending.
My heart was in my throat throughout the episode. I was terrified in the room with the incinerator that it would end there and Beckett would be shot and die in Castle arms or something. When they hugged and both closed their eyes, I thought that was it.
THANK GOODNESS IT WASN'T.
When they were in the precinct with Ryan, Espo, Vikram, Lanie, Hayley, Martha and Alexis, I was so relieved, but also still worried. The precinct hasn't been exactly the safest place in the series, despite Beckett's reassurances to Castle earlier in the episode. Any moment I was expecting a shoot-out.
THANK GOODNESS IT DIDN'T HAPPEN.
Then Beckett and Castle got back to the Loft alone, and I thought this was it. At first I was stunned that Castle was the one who got shot. Then I saw the blood pooling from Kate's jacket and staining her white shirt. And then they crawled over to each other and I thought that was it.
And then the camera panned to an empty loft and I thought we were going to see Martha and Alexis and Ryan and Esposito and everyone at Beckett and Castle's funeral/wake/memorial.
And then the voiceover started and I thought maybe there'd be a flash back in time to earlier where they were all in the precinct and the shooting in the loft never happened because they all went to the bar with the others, so we'd have a happy ending after all.
And then I realised the voiceover was from the very first episode, when Beckett rejected Castle's offer of a de-briefing, and I thought maybe this was like an 'and it was all a dream' ending, where it turns out that had Beckett agreed way back then they would both still be alive but living separate lives or something, so maybe this was showing that although they both ended up dead, they had an incredible run together.
And then it cut to seven years later and I was confused and thought that seven years after they first met, in an alternative reality (which was now the actual reality because the writers were ret-conning the show and starting over), had Beckett and Castle gotten together in S1, they would now being alive and together and with three kids, rather than dead on their kitchen floor.
And then, THANK GOODNESS, I Googled it to check and it turns out that the time-jump was exactly that. Somehow and very abruptly and without time to adjust or fill in the gaps (but hey, that's what fanfic is for), they both survived the shooting in the Loft kitchen.
AND THIS ACTUALLY WAS SEVEN YEARS ON FROM THAT AND IT WAS A HAPPY ENDING. AND THEY SURIVIVED AND BECKETT WASN'T KILLED OFF OR PUT IN WITNESS PROTECTION OR ANYTHING CRAP LIKE THAT. AND THEY WERE TOGETHER AND HAPPY AND THERE WERE LITTLE CASTLE BABIES. AND OH MY HEART MY SHIP HAD A HAPPY ENDING.
I'm not saying that the show was perfect. I think S8 was probably one of my least favourite series of the show. LokSat (or however it is spelled) seemed ridiculous the whole time. William Bracken was a much better villain and I wish they had ended that plotline with the episode Veritas (incidentally, one of my favourites ever of the show). Rick's disappearance and missing months always felt like a crap storyline. Honestly, I kind of wished they had left the show at the end of S7, because although we didn't know what happened to Castle during the missing months, the end of that episode felt like closure, and S8 felt like it was ruining that closure (another reason why I would have been PISSED if they had chosen to end the show by killing off Beckett, rather than leaving it on the lovely S7 ending).
I'm also not saying that the episode was perfect. S8 plot aside, the transition between the penultimate scene in the Loft with Beckett and Castle dying together on the floor and the 'seven years later scene' was too fast and not clear enough. The voiceover from S1 confused me to the extent that I had to Google it to check whether it 'was all just a dream'/all AU, or an ACTUAL happy ending. (Admittedly, that may have something to do with my track record with doomed ships, and also my over-active imagination.)
BUT, that being said....
Beckett and Castle have their three beautiful children (loving the flashback to the episode with the guy from the 'future' who told them, among other things, that they would have three kids :P). They survive, they're together, they're alive.
They have their happy ending. Always.
And that's enough for me.