There's absolutely no earthly way they are keeping that date. It would have had to start filming a while ago and they don't film movies without announcing them. So there won't be a Marvel movie on that date

I'm pretty sure his response is supposed to indicate that NOBODY from the studio said the trailer was going to release in December. Those were all just rumors and online speculation, we were never promised a trailer this month. Just chill everyone it will come when it comes.

I cannot emphasize how big of a mistake that would be. The only benefit that would bring is MAYBE bring in a bigger box office. That's not even certain because, as you said, the last knight made way less than the previous ones, so I don't think that's a very strong argument. Audience engagement may be lower now, but I think it's much better to have quality films over films that just make a lot of money. If Bay came back to direct that would be completely backwards and back track on the growth the movies have had in of storytelling and honoring the source material.