http://www.vg247.com/2011/05/31/e3-rumour-watch-sony-briefly-reveals-syphon-filter-4-on-their-website/
Hey, Y2Kev... hype.
Well, massive chunk of salt then folks :/
Several forums, including those published by Giantbomb, GameTrailers and French website Gamekyo, are reporting that Sonys US Playstation website published a post disclosing Syphon Filter 4 before removing it an hour later.

Apparently, the post said the game was being developed using a new engine by SCE London and would be releasing in Q4 2012.
Well send Sony an email and ask for comment.
Hey, Y2Kev... hype.
Nirolak said:I checked all three sources, and the links weren't working when any of them were posted...
Well, massive chunk of salt then folks :/