Sqare Enix has cancelled the development of Kingdom Hearts Missing-Link. According to an update posted on May 14, the company determined that it would be “difficult to provide a service that would satisfy players in the long term.”
Kingdom Hearts Missing-Link was a GPS-based action RPG meant to depict the “blank periods” of the Kingdom Heart series. It was originally announced back in April 2022 along with Kingdom Hearts IV, and was initially planned for release in 2024 across mobile platforms. Although this was delayed, there were some small-scale prototype tests and multiple closed beta tests conducted for the game in the meantime, and development seemed to be progressing. Unfortunately, it seems the project has since fallen through.

Based on the announcement, it appears Square Enix judged that Kingdom Hearts Missing-Link would not be able to retain long-term user satisfaction, and thus decided to cut its losses without releasing the game.
On the other hand, Square Enix assures Kingdom Hearts fans that work on Kingdom Hearts IV is still fully in progress.