An MMORPG based on Sony and Guerrilla Games' successful IP Horizon has apparently been canceled. The project was reportedly a collaboration between Sony and Guild Wars studio NCSoft.
Bear with me on this one. Back in 2023, Sony and NCSoft announced a "strategic partnership", and that partnership was reported to include a Horizon MMO, with leaker Kurakasis pointing to job listings for something called "Project H" (also "Project Skyline") in December that same year.
Now, however, Korean publication MTN (via Eurogamer) has reported that Project H has been canceled following a project review at NCSoft, along with several other titles in development at the company.

Of course, all of this should be taken with a pinch of salt, because Sony and NCSoft never officially announced the Horizon MMO in question, so naturally, it also hasn't officially been canceled.
However, cancelling such a project would fit in with what appears to be a wider retreat from the live service market on Sony's part. Earlier this week, the company canceled two live service games in development at Bluepoint and Bend, with the former reportedly being a God of War spinoff.
The retreat is likely inspired by the colossal failure of hero shooter Concord, which was shut down just two weeks after it launched last year. The game's developer would go on to be closed down by Sony, along with Neon Koi, previously known as Savage Game Studios.
It's also worth noting that assuming this MMO was actually in development, it's probably not the Horizon multiplayer game announced back in December 2022, as that's in development at Guerrilla itself rather than a third-party studio (although that could well end up being canceled too).

As for what's next for the Horizon series, while a new mainline game hasn't yet been announced, a live-action movie based on the property is currently in the works, along with one based on Helldivers 2.