From the real war up north, to the skirmishes in the south, the next few shots feature a Greyjoy fleet, most likely a victorious Euron, arriving in King's Landing, followed by more shots of the Unsullied's castle storming. It might only be due to trailer editing, but it again seems like Daenerys' may send her army to attack the capital -- a move that's sure to only force Cersei to do something really crazy. (Can you imagine?)
But the Greyjoy fleet arriving does seem to also imply Euron is to Cersei's aide, perhaps even offering her a prisoner of two. The two have common enemies, and besides the Night's King, they are the series' only two remaining "villains", a team up between them shouldn't be unexpected.
Field of Fire
Beginning with a shot of Daenerys standing serenely on a balcony, this montage crams in a lot of information in a very short span of time. Jaime rides across a field of fire, entirely alone and looking distressed; more footage of ships at sea exploding; Tormund battling an assailant in the north; Daenerys atop Drogon as he flies over a Dothraki horde; Theon and Yara looking up as they come under attack; back to the front lines of the Lannister army; Jon and his men surrounded by wights; Missendei and Grey Worm about to kiss; and only the second close-up on Tyrion, looking uncharacteristically uncertain.
As if it weren't pretty clear already, Jaime is going to be lucky to survive this battle with Daenerys' forces -- and those dragons in particular, judging by the flaming carnage all around him as he rides across the field at full speed. The phrase, Field of Fire, is also a significant one in Westerosi history as it's the name given to a battle in which Aegon the Conqueror, his sisters, and their dragons burned up the Lannister and Gardener armies, erasing the Gardener family from existence and forcing the Lannisters to bend the knee. Could season 7 see a repeat?
Coupled with further confirmation of Yara's fleeting getting wrecked, Jon and Tormund under attack from wights, and even that quick shot of an anxious Tyrion, season 7 is shaping up to be a most intense season -- and for Game of Thrones, that's really saying something.