Which in turn depends on the accuracy of various physical models of the universe. We still have recently encountered surprises, such as so called dark matter.
But a reasonable projection is going to have the stars all dying out. I felt there was something “existentially” wrong when I read, as a child, science books that foretold the stars burning out in billions of years. From my point of view, they might as well be scheduled to burn out tomorrow, and the lack of permanence distressed me. Only much, much, much later did I realize that was God beginning to knock on the door of my mind.
Timeline of the far future
http://en.wikipedia.org/wiki/Timeline_of_the_far_future
Things like this make me sad and feeling cold...