∆ You gotta drum up excitement.
Avant was great, but doesn't give you too much of an idea of what the general movie is. The short trailer we got last year shows some interesting footage, but it's still sort of vague. I think you need at least one "proper" trailer to be a sort of statement on what the film is (although to be fair EoE didn't have one in the traditional sense).
Even Q, which had such little marketing because it was trying to avoid showing anything of the timeskip, had the one minute "Wrath of God" trailer to set the mood and get people excited before release.
And also, we are giant Eva nerds. They could not release a single trailer, and we'd still watch the movie. But I think the more causal audience (the people who contribute to making these films so succesful, I don't know if they would do the same numbers if only the hardcore otaku went to see them, remember Q was the second highest grossing film of 2012 in Japan) right now might not even be aware that this film is coming, plus it's been so long since Q.
They need an attractive trailer that will be shared online, with some surprising/emotional component and some track of the OST. Those are the things that guarantee people will wanna go see your film. There's a reason everyone does it. And it should be some months before, to have a build up and make people excited, have time to find out about it, talk about it, etc.
I think it would make sense to follow the pattern of Shin Godzilla. One trailer that goes into the mood and establishes the tone and look of the movie. Then a trailer that goes a little more into specific scenes that you wanna see continued, without revealing too much, and some sort of surprise ("Oh shit Shin's nuclear breath is gonna be purple??").
Outside of the commercial function I think well done trailers can also improve the experience of watching the film. Mentally prepared having gotten a taste, you are in the right mindset. I at least like that. Although it's true that at this point we know Anno's style and all, but more casual audience members might not to the same extent.
Lastly, I think we will see Avant2 before the film comes out as well, right before release. I'm sure releasing Q's Avant that way was very effective, and I was surprised that we got Shin's opening scene a year before the film. I think we might see the second one (since the film does have two) days or a day before release. The first Avant was also sort of autoconclusive, while the second one might lead more directly into the rest of the film, which will also get you people wanting to see the film.
Edit: And outside of that hopefully well articulated justification for trailers...I just wanna get hype lol. Hear music from the film, see shots that I otherwise wouldn't get to see till who knows when, take screenshots, discuss the footage with others, etc. And trailers are works of art in themselves, and I am always more than happy to get more Anno-edited stuff.
Shinji: "Sooner or later I'll be betrayed... And they'll leave me. Still... I want to meet them again, because I believe my feelings at that time were real."
Ryuko: "I'm gonna knock ya on your asses!"
-Asuka: THINK IN GERMAN!!! -Shinji: Öh... Baumkuchen...
Hayashida: "As game developers, our work is special. All of us here can put smiles on very many people's faces with our work."
~('.'~) (~'.')~ Dancin Kirby