Need new passport but have applied for z already

My husband is worried that he only has 4 usable pages left in his passport and we are moving to China in a month. Will it be okay to get a new passport before we leave even though he has already applied for his z or should we wait until we get to Shanghai then get a new passport from the Consulate. At this stage he has no Chinese visa stamps or stickers yet but will a different passport number on arrival make things too complicated?. He cannot add pages to his passport as it is not allowed for an Australian passport. Thanks