So if I had to guess, the masks that got leaked are probably the content drops in the months in-between the Holiday/spring updates. With this it would mean that Hunting Grounds actually does get a free update for November and we can presume next month will be the big one. When I'm not sure since I don't know if Illfonic will get the day or week off but this is a good sign regardless that we'd see support between big drops. Probably wont be fairly large updates if this is anything to go by but it's a good sign regardless.
I guess this means the other masks that got leaked might be January and that leaves February unaccounted for. March I'd assume is when we'd see the next big update (spring) if Google is to be believed.
I didn't have to download an update for this either so I guess today all they did was turn it on so players could see it. In that case if it's not already in then we will probably know what's in February once the Holiday update hits.