Assassin's Creed 4 may take place before 3.

quote

Ubisoft producer Francois Pelland has told UK paper The Metro that it’s entirely possible that Assassins Creed 4 could take place before the events in Assassins Creed 3. Pelland says that due to the franchise being based on both lineage and DNA, the game has nothing to do with time, therefore the game could either take place before the American Revolution, or after it.

“It’s a question we’ve been getting a lot. It’s not a moving forward thing, it’s all based on lineage and on DNA and therefore it has nothing to do with time. The next game could easily go backwards as much as forward, no problem.”

quote Agent Mo

quote Intoxication

quote Agent Mo

I think people are misinterpreting this. From the quote they didn't say anything about having started development or planning for AC4, just that they're open to the possibility of it being set before AC3 is.

If they have not yet started developing AC4, then how are they going to release it by next year?

Where did it say that

quote Dragoon

quote The Pursuit

I am sure ACIV will be released not to long after III. They just love doing that don't they.

They're slowing down production after ACIII. While they'll definitely start developing ACIV before the end of the year (if they haven't already), I wouldn't expect a new AC title after this until at least 2014.