heck, no one knows if it is going to be Episode 2 or 3 when they get married, i ahve seen a Plot summury for Episode 2, and there is some spoilers in it, which i will not metion (it came from the ranch), i have also seen some artist scetches for a few scenes, again there is some spioilers there, do i mind? no b/c it is how the story develpoes, and the characters interact, which makes the movie. I never knew EXACTLY how Anakin was going to be freed from slavery, and the neat Jedi gambling dice trick, suprised me, also the MIDI-clorians did too.
anywaz back to topic
I dont think Naboo's government has a true monarchy. Amidala is queen, with advisors, but there is no hint of her trying to find a "king" and in the Novel, it said she was voted in by the people to become queen. so, who really knows.
And in case your wondering, Princess Liea is royalty to the house of Organa (her adopted father is Bail Organa) but Luke never gets any title except the son of skywalker. So i dont think either Luke, or liea is royalty by blood, so i am thinking that Anakin will not become king