The number seven was chosen because the Greeks believed it to be the representation of perfection and plenty because it was the number of the five planets known anciently plus the sun and moon.
I am stoked. The First movie about the Silmarillion is coming at 2018. The title of the first movie will be: "Ainulindalë" Read here. Official news by Peter Jackson and New Line that the Silmarillion will be made into a series of movies.