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.”