The scenario is that Cortex burns his ships, marches into Mexico, and is never ever seen again. Assuming this is enough to either keep Europeans ignorant of the mesoamerican wealth, or too scared to attempt another large scale expedition anyway, how would a surviving Aztec (or similar) empire look as it developed through the centuries? Would the religion survive or is it likely to adopt a form of Christianity? Could the loose alliance of city-states and corresponding vassals that formed the empire centralize?