The main problem is the occupation not Hamas ruling Fatah. The division between Gaza and the westbank is temporal. If the world recognized the results of democratic elections in Palestine, this would not have happened. Once Pals get their state, no one has any actual motives to continue this split. Even if it continued, its an internal issue.
Man and woman arrested for attempting to attack Israeli forces in Jerusalem's Old City (Haaretz)
from the article: Obama to Abbas: I am committed to creation of Palestinian state