Rumour has it as a full sequel of PSP Syphon Filter: Logan's Shadow, and is being handled by SCE London Studio. We should "expect a launch" Winter 2012.
"Syphon Filter 4 is slowly gearing up for a release on PS3. Expect a launch for Winter 2012," reported the Italian OPM. An alleged leak on the US PlayStation site was quickly plugged but not before detailing a Syphon Filter sequel with a rough logo a while back.
Are you eager for more Syphon Filter, videogamer?