Since the "royal family" gave out the power of aldnoah, if the king dies, wouldn't that remove the aldnaoh power from all the dukes etc etc since he gave them the power? I'd presume only the princess/bloodline of the royal family would still have their own power still, but that would kind of end it quick, considering he does seem to be old/dying as is anyway.
Pretty much king dies, only princess has the power, everyone else loses the power. Unity between mars and earth with princess using her powers to bring both together using that spaceship, everyone lives happily ever after.
/randomthought