I think that discussing about whether Serena might stay on, or whether Ash would continue to the next region at all, or such stuff is not worth at this point. We are still just 60 episodes into the XY saga, and while the various routes that the writers can take at this point are closing down one by one, there are still plenty. So let's discuss that at around XY120 if anything.
See...the ship can be canon too without affecting their culture. There are more than enough examples of animes with canon relationships. It is just that we need to understand the constraints of it, and adjust. And frankly, it isn't like it would be too much for us to think of it in their perspective. Like I mentioned, the subplot of Pacific Rim was perfectly understandable and incontrovertible at the end. Similarly the subplots of Naruto and the other animes were also more than satisfactory. So why not for Pokemon too? They are thinking of the worldwide fanbase. But that doesn't mean that they would bend backwards for us, especially when they really don't need to.
I respect your opinion; however, my first point was to reply to what another person commented lines below, remember that we get new members and they have the right to talk about their expectations if related to the topic.
Regarding your second point, I agree. The examples you provide are good examples. I don't think they will bend backwards for us, but they can do it to break their "adventures of a 10 y.o. boy" plot.
The last episode, in my opinion, was very emotional and showed us how much Serena loves Ash.