Most likely Teaser because shooting for S5 will still go on till Jan 2025, (without post production which will take another 2 and half months) and not all scenes are shot in order so releasing First half of S5 and trailer does not seem fit. Behind the scenes they have already done 2 videos. Promotional stuff and teaser are most likely. \
But to make it memorable, maybe a collage of all the 4 seasons highlights in one video.