This is the seventh film in a series that has been pumping out one film every 2 or 3 years. I understood the growth from 5 to 6, but I don't see why that would happen again. FF6 was already a hit in China, so there won't be huge amounts of growth there. Sure, it'll gross more, but that's not going to cover the $150-200m extra it needs to make $1b.
Paul Walker's death won't make much of a difference, by the way. He wasn't a well established actor outside of this series, so his fans will show up either way - and although his death did get the film some awareness, that was 1.5 years before the movie comes out.