Knowing about a land and utilizing it are two different things. Baffin Islands was known by Europe since the Greenlanders stumbled upon it, yet nothing was done with it. As for Antarctica, Portugal would try to claim it but others would come in and set up whaling stations on various subantarctic islands. If anyone discovered gold, it would make for a brutal penal colony.
It doesn't really matter whenever Antarctica is dicovered and by whomever. It's still a frozen desert with very little economic potential outside of whaling.
The continent will still remain unclaimed and will but superficially be explored until the early 20th century... when there's nothing else left to claim and explore.
Portugal might snag a couple of Southern islands for whaling stations, but that's about it. You can't exactly do anything with Antarctica until you get to late 20th Century technology at least.
Quite the contrary to the general consensus, any slight change to the history of Antarctica could have huge repercussions. Having formal recognized claims and sovereignty exerted over the continent could have easily resulted in mining and oil discovery in the 20th century which would have significant effects