Courtesy of the Japanese website.
The official Japanese website for Shin Megami Tensei V has provided us with more information on the upcoming game. (This is not available on the English version of the website.)
Making a return will be the the Press Turn System and Demon Negotiations. (The Press Turn System gives you an extra turn if you’re exploiting a demon’s weakness.)
Demon Fusion will also be making a return. This will allow you to fuse demons to create even stronger demons. You’ll be able to consult with Sophia, a new non-player character, to fuse your demons. There will also be a level up system.
Finally, players will have a small amount of choice which will effect the ending of the game. But no further information on this has been revealed.