I’m deeply invested in iMessage portability but I think you might be mistaken. It was FaceTime that was announced as a to-be-open protocol but didn’t see the follow-through.
I don’t think it had anything to do with their earlier promise (and I’m also not convinced patent issues were the real crux of the matter ten years ago).
Not really; Apple simply doesn't move that fast. You can certainly see projects get more resources as a result of trends, but that isn't necessarily going to move the release forward a year.