From the article:
Abrams is eager to have the original characters in the lead roles and introduce a new generation in supporting roles.
The new plan will see the offspring of Skywalker, Solo and Leia introduced in 'Star Wars: Episode VII' before taking lead roles in the already announced eighth and ninth films.
Makes sense to me. The Big Three™ will definitely be the Big Draw™ in E7. A focus on them is what plenty of casual moviegoers will expect to see. To me, that's better than heavily promoting them (because they will be heavily promoted regardless), then having them only as minor roles in the film.
As unlikely as it may be, I agree that Weaving-as-Thrawn would be impressive.