Killzone should have been the Halo Killer for Sony, but the result was a little different than they expected. Great graphics, effects, but rough gameplay. Guerrilla would need to hire a better director for Killzone (among other things).
Killzone 4 could be a Orbis/PS4 game. Sony could unveil the game this month (February 20) and release it by the end of this year. Guerrilla Games would repeat their developer work.
This Year is going to be the Killzone year. We’ll have Killzone Mercenary (PS Vita) on September and this one, for closer to the 2013 end.
Speaking about Guerrilla, the group should be working in a new IP too.