Hello, dear nonnie! Sorry for taking so long to reply. I hope you like my answer, though I’ll try to be as honest and realistic as possible.
A couple of weeks before the season 9 finale, somebody asked me a very similar question. In that case, they asked me why I thought the chance of canon Destiel would happen and when. I’m going to quote something I said in that ask:
"I know many people have lost faith and think canon Destiel won’t happen, but I remain confident. I don’t know, however, when it will happen. The only thing I can do is try to predict. I can give you my reasonable prediction and my shipper one. You choose which one you prefer."
My “shipper prediction” was that a good moment was the season 9 finale and I explained why I thought so. The narrative was leading us to something important. Now that I know how season 9 ended, I don’t feel disappointed at all. The narrative took us to something that is totally canon: EVERYTHING CASTIEL DOES IS FOR ONLY ONE HUMAN: DEAN WINCHESTER.
Of course, we have always known that. Cas has said again and again that he does things for Dean or because of Dean, but what was different this time? Metatron’s phrase! "His weakness has been revealed. He’s in love… with humanity." And the same Metatron says, in the season finale, that in Cas’ case, everything was always to protect one human. Soooo? 2 + 2 = 4. The show basically yelled at us: Castiel is in love with Dean!! I was satisfied with that.
My reasonable prediction around 4 months ago stated this:
"Destiel will be canon till the series ends. They might continue toying with the idea, leading us to hope and believe but won’t do anything explicit because they will wait till the last second. Why do I say that? Because Dean and Cas are endgame and NO ONE will change my mind about it. Dean and Cas are going to be together at the end of the series even if Destiel is never canon, simply because they belong together. I just hope the show is brave enough to make it canon, because if they just pull some kind of ambiguous crap that will be open for interpretation, it will be the most disappointing thing in the history of television. (Sorry for the exaggeration!)."
I continue to believe the above paragraph. (In fact, I’ve written a little something about what I think the endgame should/would be). We already know that there is a huge possibility for season 11 and maybe even season 12. The longer the show takes to end, the longer it will take for Destiel to be canon the way we want it to. The show will NEVER explore a romantic relationship between Dean and Cas. If we expect that, we should better look for fan fiction right away. They will definitely continue teasing us. That’s the television business! And noooo… I don’t think that’s queerbating because no one can say that until the very end of the series. I’m totally sure they will give us something more in season 10, something that will make us happy because TPTB are not THAT stupid. But 100% acknowledgement the way we want… I wouldn’t expect that in season 10 unless something happens and we learn that it’s gonna be the last one.
For season 10, I expect some kind of resolution because it’s the end of the 3-year story arc Jeremy Carver had, but I don’t expect Dean and Cas to be together in a canon romantic way. If there is an 11th season, we can expect more conflicts, and we can definitely expect our two assbutts to continue floating around each other, but that’s it. This is Supernatural we’re talking about. We have never even had a female/male happy relationship on the show. How can anyone expect that for Destiel? Impossible! Dean and Cas are endgame, so we need to be patient and decide… Do we want more seasons or canon Destiel? Because in my eyes it’s very clear: once they are canon, they show will be over (not because the ratings will drop or something like that, but because the people in charge will wait till the last moment just to be safe).
Of course, this is pure speculation on my part. Some people may agree, some may disagree. That’s why I don’t get frustrated anymore. Hannah/Cas or *insert female name*/Dean… that’s just nothing for me to worry about because I love Destiel, but I keep my perspective totally based on the reality of the show and what TPTB could and could not do.