Not making a new killzone was the best idea ever. the team would have been sick of making the same game over and over.
This has given them a new lease of life. Maybe develope another killzone now and possibly make it semi open world? And their next game after can be Horizon 2 to launch on the ps5. That would be an awesome exclusive to push the ps5 and it would have mega hype after the reception Horizon is getting!
naaa. they should just leave killzone behind. its done for. make Horizon 2, and start developing a new IP after it with a small team, while the majority of the studio works on Horizon 3. release Horizon 3 then the new IP.