Edge Magazine is reporting in their new issue that the "bulk" of Guerrilla Games' staff is developing Killzone 4. In the issue, Guerrilla studio founder Adrian Smith stated that Guerrilla has "got to continue the Killzone franchise," then added, "We're at 160 heads now; we're looking to get to about 190 to 200 within 12 months. That may or may not happen because of our benchmark."
If that weren't enough, a brand new IP is also reportedly being worked on. "An embryonic new IP is growing within the studio for the first time in seven years," according to Edge. "Additional staff cycle in from the Killzone team for brief stints to lend their expertise."
The only real question is if Killzone 4 will be a PlayStation 3 or PlayStation 4 game.