So GG have made horizon zero dawn which took a lot of time to make , it is really great but I feel so sorry cuz I havn't got a new killzone game , so lets try to make new ideas for the next game , what we could expect , what GG should avoid , what is gonna happen to story , MP , and a 3rd mode
Unfortunately, I think Guerilla Games has abandoned the series...
However, if Guerilla were to make a new Killzone game, the game should feature new movement mechanics that make the Shadow Marshalls(assuming we will continue playing as them) seem as a more elite force than a normal ISA soldier. Maybe add hoverboots/a more advanced jetpack, leaning, and different melee weapons. Weapons should be more unique and varied instead of the normal shotgun or assault rifles we are used to. How about weapons like a net launcher(traps enemies in a net), sniper rifles that disinegrate enemies, assault rifles where the lasers can bounce off walls, and maybe an explosive crossbow type weapon. These weapons would differentiate the next Killzone from other shooters.
I have only played Shadow Fall, however I think in the next Killzone the player should alternate between playing as Echo and as an ISA agent trying to hunt down Echo and the Helgast. That way at the end of the game, you have to pick who lives: Echo or the ISA agent you play as.
Multiplayer in Shadow Fall I thought was good; I think they should keep it mostly the same. They should just add more maps and maybe add environmental damage and vehicles? Also make the ISA have some abilities that the Helghast do not and vice versa. For example the ISA could have increased mobility and running speed, while the Helghast have increased health.
A third mode should be a two player splitscreen offline or two player online mission mode(kind of like MW2 missions) where two players play through sections of the campaign with two players. Or Guerilla could just make a horde mode with four player splitscreen/online like every other shooter.