Since we’re adding reasons, I’ll add mine as well. Though to be honest, I don’t really think a lot about Jon surviving, only about Dany. But I think that if one survives, the other survives as well.
For Jon, he has a lot of foreshadowing for being king in the books. One could argue that this foreshadowing is just to give hints to his true parentage, but I don’t think so. There’s a meta about this here.
It’s not as easy to find foreshadowing for Dany as queen, because she already is a queen, so her being referred to as queen doesn’t really say anything. But Dany is doing many of the things Jon is doing (mentioned in the meta above), their training to be rulers has been similar. Plus, I always felt like this quote was foreshadowing for Dany as queen of Westeros:
Her brother smiled. “Good.” He touched her hair, almost with affection. “When they write the history of my reign, sweet sister, they will say that it began tonight.” - Daenerys I AGOT
I always interpreted it this way: Viserys is thinking that people will write about him as king of Westeros. But it will be about Dany’s reign that people will write about, her reign that began that night.
I also don’t think Dany’s character arc is about sacrificing herself. She has been selfless from the very beginning of the story, so to me, deciding that she has to sacrifice herself in the end is not character development, it’s stagnant, because Dany always was self sacrificial. I think she has learned about ruling, that’s her character development. Even her choice at the end of ADWD, of choosing war and fire and blood, that people use to argue that Dany could never be a peacetime queen, is in my opinion simply part of her character development to have a more mature view of peace and war and be a better ruler, not a sign that Dany can never rule in times of peace.
I also wrote why I believe Dany will survive in different posts:
This one talks about how Dany will bring social change to Westeros, and how i think she and Jon are the only ones that could do that.
This one and this one talk about the positive interviews about the show’s ending.
These are my observations about the trailer and why the trailer makes me think Dany will survive. Besides, Dany is very likely pregnant. I think there must be a reason for all the baby talk in season 7, and if Dany will be pregnant, then she can’t die before boatbaby is born. But Dany is not showing in the trailer. This means that not a lot of time has passed in the season, and that Dany will only give birth later in the season. If she’ll only give birth later, then she can’t die in a battle before this. And I don’t think Dany dies in childbirth. So to me, it looks like Dany will survive to have her baby in the end.
Also, in GRRM’s original outline, Dany and Jon survived. Many things in the outline changed, of course, but many stayed the same. GRRM was asked if he ever changed the ending of the books, and has stated several times that he didn’t change the ending (though I’m really lazy to look for the interviews, but I did watch interviews with him saying that), so it’s a strong possibility that Dany and Jon will survive.
Though, of course, it’s still unclear how similar the books and the show will be. He said in a recent interview that there will be differences (and in other interviews as well). But he did tell D&D the ending, and in a recent interview, he did say that some of the things in season 8 are based on what he planned and that he got emotional about it 20 years ago. So I’m expecting that, while there will certainly be many differences, the major plot points will be the same. So because I expect Dany and Jon to live in the books, I also expect her to live in the show.