It should go back to being the Seven Kingdoms once again. Which really is what should have happened when House Targaryen originally fell. I could never understand why Tywin wouldn't have wanted to be King like his ancestors. Robert didn't really care. He would have accepted remaining leader of the Storm Lands and Ned could have gone and buried his head in the snow.
I don't want Westeros to go back to seven independent kingdoms, because those seven kingdoms were always at war with each other. The population as a whole is better off with a king and a central government, simply because the king can moderate disputes between great lords and reduce the number of battles and wars and innocent civilians killed or suffering economic devastation.
Personally, I hope Tyrion is named king and Sansa is told that she's queen whether she likes it or not, because they need her to do the ruling when Tyrion is too hammered to make decisions. They'd be excellent co-monarchs!