No every site is not closing. If you are referring to turn over then its about on par as usual. People buy domains the sites do not turn a profit, people lose interest, incompetency etc. As far as file hosts closing very few have closed, they just cut off the "professional uploaders" and I use that term extremely loosely. Long story short, the world is not ending, there is nothing out of the usual occurring.
Just search online for "dropped domains" and you will see how many sites close daily. And that is just those that have elected not to extend there domain name.