The B747 has survived much worse in the past (Air China 006 stall in 1985 pops to mind). That pulled 5g before being recovered and landing safely. Very rugged and capable airframe for the B747 (wonder if modern aircraft can do likewise?). The ATSB investigation will find the root cause but superficially sounds like autopilot error combined with some strange wind conditions (maybe shear). QF pilots also have a reputation for being exceptionally competent, I'd have been happy to be on that plane.