Captain Marvel has been discussed quite a lot and going by the looks of it, one thing can be said with conviction that she will have some major responsibilities in the movie Avengers: Endgame. And going by the reviews that are circulating, she is by far the most powerful avenger in MCU.
Back in September 2018, the producer of Captain Marvel, Kevin Feige had stated, "She is more powerful than any character we've introduced thus far. So that alone tells you that there's a reason Nick hit that button at the end [of Infinity War], when he realized that they were up against something far bigger than they had ever been up against before. And having her on your side is hopefully going to change the balance of power in a way that they desperately need."
Now, if someone gets highly praised like this considering Thor with Stormbreaker seemed to redefine power levels for characters not wielding any Infinite Gauntlet, is something noteworthy. If we delve deeper then it can be proved that CM is a threat to Thron unlike no other avenger because of her affiliation to Tesseract aka Space Stone. Despite the main ability being manipulation of dimensional space and motion, it's main power lies hidden in the fact that it emits special energy that is unique to the other Infinity stones.
That energy can be harnessed and used by replicating it and contributing to the empowerment of others. There have been cases earlier which showed HYDRA's capability to extract power from objects such as the Tesseract and also with Loki's Scepter. In fact, HYDRA's experiments with the Mind Stone led to the awakening of Quicksilver and Scarlet Witch's abilities which was the explanation to how Scarlet Witch could destroy the Mind Stone in Avengers: Infinity War.
And since the trailer already shows an explosion that gives Carol her abilities, chances of Carol sharing a link with the Space Stone's energy are high. Apart from this, Carol's most undervalued ability to absorb power will come in really handy. By doing so, she can unlock her Binary form and that will come in really handy when fighting against Thanos.
More than that, her energy absorbing capability will absorb all the energy from the Infinity Stone. And if she is used in this capacity then she can really be the X-factor in Endgame.