According to a 4-page spread in the new issue of the Official Playstation Magazine UK, the upcoming Killzone game for the PSP (entitled Killzone: Liberation) will not be a first-person shooter like its PS2 and PS3 bretheren. Rather, it will have a camera style similar to Metal Gear Solid.
Along with the new vantage point, OPMUK reports that you will play as Jan Templar attempting to liberate hostages from behind enemy lines (hence the new subtitle). There will be a focus on stealth and keen use of the environment to avoid and take down your Helghast rivals, which also happen to come in several new forms. You'll get a few new weapons to help you out, though, like a crossbow.
If you have access, check out the new OPMUK for screenshots and more detailed information.