In a statement given to Brazilian site TechTudo, CEO of Ubisoft São Paulo Bertrand Chaverot has said that Ubisoft is researching Brazil for a possible game or at least scenario in the Assassin's Creed franchise to be set in the country. Here's Google's translation of what Chaverot said to the site:
The development team already has several ideas on how to build a scenario based on a particular moment in the history of Brazil and that fits perfectly in the millennial plot between Templars and Assassins, but so far nothing is decided.
The statement comes after Chaverot made a public apology to fans for what was viewed by many as a negative portrayal of Brazil when Desmond briefly visits the country in Assassin's Creed 3, and the site is understandably keen on the idea of an Assassin's Creed game that might redeem Ubisoft of its apparently negative views of the country. But it's important to note that the process of making a new Assassin's Creed game involves research into various potential locations and time periods before any decision is made.
Besides which, it looks from the survey Ubisoft recently conducted that the developers are considering repeating what they did with Assassin's Creed 2, with a couple of sequels featuring Connor before they move onto a new character, time, and place. And it's really not worth even considering the possibility that after spending so many years on Assassin's Creed 3, Ubisoft is going to rush production of an Assassin's Creed 4 set in Brazil and get it on shelves by the end of next year, so don't get your hopes up.