Gabriel Stanford-ReisingerGuerrilla Games putting a focus on the Horizon series and leaving Killzone behind was a deliberate decision by the studio. In other words, it was done with the series as a team.
In a Washington Post interview, art director Roy Postma, a 24-year vet with the studio, revealed the team simply didn’t want to work on the series anymore, wanting a refresh and the much more vibrant and colorful world of Horizon was its way of escape.
“We were done with it as a team, as a studio, we needed to refresh the palette. It was, by choice, the opposite of Killzone.”
Unfortunately this paints a very bleak picture to the group of people who held onto the very slim chance of the series coming back, but unless Sony gives the project to another studio, we highly doubt the series will continue and its legacy has ended with 2018’s Killzone: Shadow Fall.