The debut trailer for Shin Megami Tensei IV is included as a bonus in the 3DS Devil Summoner: Soul Hackers remake. Soul Hackers officially goes on sale in Japan later this week, but people have already been snapping images of the trailer and posting them online:
More images can be found at the above link. Keep in mind image quality is based on people taking pictures of their 3DS screens.
EDIT: And the full trailer is now online for your viewing pleasure.