TFA definitely has a good shot at dethroning Avatar, but it's still a huge task. It's a bit of a shame that such a mediocre movie sits at the throne, but what Avatar had that Star Wars doesn't have is the whole spectacle angle and in pretentious words "it's more like an experience than just a film", which in contrast TFA doesn't have. Then again, Star Wars comes with pre-existing fandom and has other perks.
TFA is gonna continue to drop, but there's still not a lot of big movies coming anytime soon. Kung Fu Panda 3 is the first movie that will dethrone Star Wars as nr1 for a weekend, and that one is still 2 ½ weeks away. Even with that one out, there's not gonna be a lot of big non-animated films out, with a few like Deadpool in February and then Batman v Superman in March coming up. I still think there's plenty of people who have waited with TFA until the initial craze wears off, and there's also people like myself who will most likely go a 4th or 5th time.
2.7 billion is a tall order but it's not over until it's over.