Well, I suppose the first point is that there are hot spots and cold spots, and gradually everything will become more and more homogenous.
The big question is, in our expanding Universe, is more matter/energy coming into existence to fill the extra space, or is the supply already fixed and is it just going to be stretched thinner and thinner, and thus get steadily colder and colder? Various theories exist on this one.
As you cannot destroy energy, the Universe can never become completely cold, 0ºK, but it can become very chilly. Face it, most of it already is.
Knowledge comes, but wisdom lingers.