Star Wars is the most culturally significant film franchise in the US. That Disney marketing machine is going to be in full force for the 2015 Holiday season. Toys/collectibles, interviews, extensive media coverage, probably lots of theme park promotion, etc. If Abrams & co. deliver in the quality department, SW7 definitely has a real chance at topping Avatar. Giving the film TPM's ticket sales (if it is a quality film, I do believe it can be the first film since to cross the 80 million ticket threshold) and adding on the average 3D/IMAX boost gets it right at $750 million, actually.
If you don't admit that it is at least a very solid possibility, you're in denial.