Setting aside the suffering, and the potential impact on a depressed global economy, the interesting development related question is how will China’s political and social institutions fare through the political stresses caused by a slow down?
Indeed, Rodrik et al’s growth accelerations paper suggested (to me at least) that growth spurts can happen in poorly governed countries but sustained development, which means dealing with the wobbles on the road, is much harder to maintain. What’s more, Rodrik provided pretty convincing evidence in One Economics that democracies weather economic shocks considerably better than autocracies, which doesn’t bode well for slow down in China.
An optimist might hope (I certainly do) that the Chinese government responds to the pressures generated by economic downturn through democratic opening and redistributive transfers to the poor.
But a pessimist will remind you that there are many, many other potential outcomes.