The French colony in Brazil was established as a haven for Huguenots. If it's successful (the removal of the Portuguese is not enough-there's still a lot that can go wrong for that colony) it could provide an outlet for Calvinist settlement not only from France, but from other parts of Europe. In France this could make the Wars of Religion a little less drawn out and serious-a lot of people may decide to go to Brazil instead of fighting it out.
If the colony is successful, Catholic settlers will probably start coming as well. This may result in the colony being split at the request of the Calvinists, so that they're not overwhelmed by the 'enemy' religion. Ironically, this will make them more loyal to the Catholic motherland-they need it to adjudicate in their disagreements with the Catholic colonies.
Finally, 'Antarctica' will be the name of the colony and any countries that come from it (France Antarctique), meaning that our southern continent will have another name ITTL.