Kingdom Hearts IV is in the works. During an event in Japan to celebrate the 20th-anniversary of the series, Square Enix announced the upcoming game. You can watch the trailer in the video.
The trailer doesn't start with Kingdom Hearts IV until 4:09, so you have to skip to the 4:09 mark to see it.
Once the trailer opens, you will see Sora wake up inside of an apartment as what appears to be a giant heartless sets foot in the city. Sora uses his Keyblade to move towards the enemy. At the end of the trailer, Goofy and Donald Duck face-to-face with an unknown threat.
The trailer contains development footage that is subject to change, but the art style looks a lot more realistic.
There is no word on a release date for Kingdom Hearts IV. In August, Kingdom Hearts Missing-Link will be available as a closed alpha on both phones and tablets.