You then see core character Alisaie fighting against what looks to be a dragon-like monsters as the world around her burns. The trailer shows the Warrior of Light (your character) walking on the moon of your realm followed by the map of Eorzea being burnt.
You can watch the trailer from the livestream below (be aware that there may be spoilers in the trailer). During the Final Fantasy XIV announcement showcase, the next expansion for the MMORPG was revealed through a teaser trailer-it's called Endwalker and it's set to launch in Fall 2021.