Eschatology is the study of last things. It is a very important subject, which people rarely study.
I am only going to consider two rival eschatolgies, Christian and materialist/atheist. I'm not going to differentiate between rival Christian theories.
The materialist asserts that nothing exists except what we can observe in the material universe (or that anything outside the universe does not matter). That means the end of humankind is bounded by the end of the universe (probably well before half of all protons degenerate, 10e36 years - most of the stars in our neighborhood will have run down in 1e10 years...). There is no hope here. That's kind of depressing (at least it was to me).
Christians believe that Jesus will come again (because He said He would). At that time, He will restore life to the universe. That is where our hope comes from.