Not only do we know that the universe is expanding and have known this for decades, but in light of recent (~10 years ago) evidence we strongly think that the universe is expanding at an accelerated rate. This is widely thought to be due to the existence of eccentricities, namely dark energy, that we know nothing about. In fact we only really understand a few percent of the 'stuff' that makes up the universe. As a result, it is impossible (and probably irresponsible) to propose what will happen to the universe before we know more. I think that TV shows about this subject are good but too often they give that impression that the physical community really understands more than we think we do.