I get where you are coming from but I just don't think killzone is something that can revived to be a blockbuster franchise. As solid as the games are, they carry a negative sentiment and the vast majority of fans and media just roll their eyes when a new one is announced. I think the killzone 2 PS3 reveal debacle and Sony trying to market it as halo killer in its early days are the reason for the negativity. Maybe they can try with a new ip but the chance of success in that genre is pretty low compared to others so I don't think Sony will go down that path for the foreseeable future. I personally was a resistance fan and I sadly don't see that coming back as well. Insomniac really should have doubled down on that coop stuff from resistance 2 for the third game because it had a very good sp campaign that was criminally overlooked.
Bringing back Resistance makes the most sense imo. The lore and alternate history it plays with is much more interesting and can lend itself well to a character driven story with themes that differ from the ones you typically see today. Plus the co-op was hella fun lol.