On July 23rd, 2016, Marvel released teaser footage of Guardians of the Galaxy Vol. 2 during the 'Guardians of the Galaxy' panel at San Diego Comic Con. However, despite being publicly shown, no footage (yet) of the teaser has been leaked online. According to James Gunn, the director of the film, he stated that the teaser was an only "Comic Con exclusive" and that the footage was still in testing of the CGI and graphics.
. Eyewitness Accounts of the Footage
According to Screenrant.com, they have a synopsis of what's happening in the footage:
The characters Groot, Yondu Udonta, and Rocket Raccoon make their return, but are trapped in a prison-like cell by the Ravagers. Rocket and Groot escape from their cell to find Yondu's fin, which controls the remote arrow like in the first film. They succeed into getting it and then kill the remaining Ravagers.
The other teaser shows the Guardians gearing up and battling against inter-dimensional aliens. Along with that, new member Mantis is introduced. The final clip of the teaser shows Kurt Russell's character, Ego, who tells Star-Lord that he is his father, along with making a male genitalia joke when Drax asks Ego about him taking human form when he went to Earth.
It seems that we have to wait until May 2017 to see the final result of the film. However, the San Diego Comic Con teaser footage has yet to be leaked onto the internet.