This image popped up on Duuro.net, a website run by Krist Duro who "loves gaming and alcohol" and didn't point to the source, which ultimately means the author's suggestion of an impending Far Cry 4 where player's take on the role of Far Cry 3 villain Vaas seems like total garbage.
Duro writes "Real or Fake?" Let me answer that question for you right up front. It's fake. Duro probably made it, or someone he knows made it and he posted it.
With Far Cry 3 following the franchise's previous games in not sharing a locale or character, why would Far Cry 4 be any different? There are also some continuity issues in bringing Vaas back for another game.
Other internet users have pointed out that the image includes a date written among the quotes from the previous game: April 4th, 2014. Of course, this date seems too close to the newly delayed Watch Dogs release to be a release date. It could represent the date Ubisoft will further detail or properly announce the sequel... but I still think this image is all wrong.
In fact, it reminds me of this video from Ubisoft promoting Far Cry 3. In it, Vaas voice actor Michael Mando gets into character for a live-action interrogation scene... though even this video is a little strange too. Some of the other prisoners call the white dude Jason (Far Cry 3's protagonist) and then Jason says something like "we'll use whatever he says". It's just a stupid promotional video playing into the "insanity" motif Vaas represents.
Bottom line, this whole Far Cry 4 rumor isn't getting picked up anywhere on the internet because it's likely fake. Since Krist Duro can't give us a link to his source or detail any information about the origin of the image, I won't bother to link back to him either.