The official Boruto: Naruto the Movie began streaming the full trailer for the movie revealing the enemy named Momoshiki. Boruto and his new team mates, Sarada (who shows her Sharingan) and Mitsuki as part of a three-man cell with Sasuke Uchiha being their teacher. The new enemy, Momoshiki, is also revealed who launches a surprise attack on the Hidden Leaf village.

The associated text from the video says:

Narrator: In the place where leaves dance, the fire still burns. The fire casts shadows over the village, and the leaves bud once more.
Boruto: Shadow Clone Technique!
Sasuke: So, you’re Naruto’s son?
Boruto: Take me as your student! I’ll defeat my dad!
Text: The Chūnin Exams start!
Sarada: Boruto, you idiot. It’s me who’s going to become the Hokage!
Text: A new generation fights.
Boruto: I’ve never wanted to be the Hokage. If you were going to become this kind of parent, then you should’ve said so from the start!
Text: Danger comes to the village.
Naruto: Sasuke, I entrust him to you.
Text: An inherited resolve…
Text: Theme Song: “Diver” by KANA-BOON (Ki/oon Music)
Boruto: Isn’t there an easier way to get it?!
Sasuke: Naruto could do it.
Boruto: Why do you worry so much about me?
Sasuke: You’re more blockheaded than him. And also…
Naruto: You’ve done well. I’ve been able to watch over you as you grow.
Boruto: Useless old man.
Text: Chief Production Supervisor: Masashi Kishimoto
Man: You can’t run from us.
Text: A great masterpiece from the original creator.
Naruto: The times may change, but the essence of being a ninja hasn’t.
Sasuke: I believe that.
Boruto: How much does it take to go this far?
Sasuke: You’re my student.
Boruto: And my son.
Sasuke and Naruto: Go, Boruto!
Text: The young child (Boruto)…
Text: Will go beyond…
Text: The legend (Naruto).
Boruto: Just watch me, you useless old man!
Naruto and Sasuke: Boruto -Naruto the Movie-
Boruto: I’m not gonna lose!
Text: “I can’t draw anything better than this!” – Masashi Kishimoto
Text: August 7 (Friday)
Text: The strongest present in the history of Jump movies!
Naruto: When you watch the film, you’ll get a special manga and a full-color version of the last chapter!

Shueisha’s Weekly Shonen Jump magazine also reveals the tagline for the film being “The curtain rises on the legend that will surpass all!!”, the tagline on the poster shown on the page says “Go beyond the legend. Take the reins of the new era.” directly correlating to Boruto taking over from Naruto in being the hero.

The Shonen Jump magazine also describes the story of the new as follows (contains spoilers!):

Boruto is the son of the seventh Hokage Naruto who completely rejects his father. Behind this, he has feelings of wanting to surpass Naruto, who is respected as a hero. He ends up meeting his father’s friend Sasuke, and requests to become… his apprentice!? The curtain rises on the story of the new generation written by Masashi Kishimoto!

Source: ANN