Pretty much all of the big blockbusters these days are PG-13. All of the Marvel movies have been PG-13 and Disney has had no problem marketing them to kids.I somehow doubt the new Trilogy would be PG-13. Considering the ages a lot of the people involved with these projects were when they saw them....10 years old (I was minus one day when I first experiance Star Wars...from the womb. I wanted out after that I am told). PG is likely because it is Star Wars. The massive, mega toy tie-in money maker. What studio would want to limit their money intake from children's parents by making it PG-13? Disney??
I'm pretty certain the new SW movies will all be PG-13, unless they decide to go for a something a lot more kiddie and go PG. If anything, I think going lower than PG-13 would be more likely to scare off some of the pre-teen and teen non-fans who aren't going to want to go to a kiddie movie.
These days most of their animated stuff is PG. Frozen, Wreck it Ralph, and Big Hero 6 were all PG.
At this point the G rated movies tend to be stuff geared at a very young audience.