It's hardly written in stone but it appears to be a possibility.
Ubisoft Brazil managing director Bertrand Chaverot told Techtudo that the next Assassin's Creed installment will adopt Brazil as its setting.
If you've played through Assassin's Creed III , you know there were a few missions set in South America, so this may not come as a huge shock. However, to have an entirely new entry centered on Brazil seems like a somewhat odd choice, especially considering the previous locations: Medieval Constantinople, Italy during the Renaissance, and the Revolutionary War in this country. Perhaps Brazil has some great history of which I am currently unaware, but it's hard to believe that it can compare – at least on the prestige scale – to the previous environments.
Where would you like to see the next assassin go? What time period would you be most interested in learning more about and virtually experiencing?