Avatar is at almost 2.8 billion dollars. That is such an absolutely insane number that it is unknowable how it achieved it, and unpredictable what will surpass it. There was fucking magic at work to get that insane of a number. There is no equation of Star Wars + Awesome = Avatar Numbers. That's too simple.
I will say, the best thing Star Wars has going for it (outside of being Star Wars) is that it's releasing in the winter. It could potentially pull a Titanic and just hang around for months. I'm curious of Disney will second guess moving Episode 8 to the usual summer blockbuster slot is 7 proves some real magic can happen releasing in the winter when the field is wide open.
I think Avatar was special. It was a great film, but it was special in that it herralded the return of 3D to the theater with an experience that has yet to be topped as far as 3D goes. The quality of the 3D itself lended the film to multiple viewings to experience it over and over again with friends and family. It single-handedly sold 3D televisions.
Now. Star Wars is unquestionably the more valuable franchise and brand and lots of people will go see it in IMAX 3D...but how many people will? People like me will probably see the movie more than once because it's awesome, but how many will? It damn near has the Christmas holiday all to itself, so how well it goes from Dec 17-Dec 31 will tell us quite a bit about its trajectory.
One thing is certain: Disney clearly believes they have a film worth pouring (and I mean *pouring*) money into as far as marketing goes and tbqh, they haven't misstepped yet. This is a well-executed, well-organized marketing push and has been since the very first teaser trailer. Disney isn't fucking around and the directors and writers appear to have hit all the right notes if these trailers and comments that have been made are any indicator.
Things that could hurt this film:
1.) It's bad. That's the first and foremost. If it can't be considered objectively better than the prequils, it will start fast and fade quickly.
2.) It is pirated. December is right around the time when companies are sending their disc copies to the academy for awards consideration. That usually means everything through December is leaked at the end of December or early in January which could cut deeply into repeat watches and international numbers. This wasn't as big an issue in 2009 for Avatar, and people wanted to see it in 3D anyway. Star Wars is not defined as an experience by 3D so not seeing it in 3D will not be a discouraging factor for pirates.
So that's it, IMO. It *could* approach Avatar numbers, but a lot of things have to break right for that to happen. Now...Age of Ultron on the other hand...LOL.