Baring unknown physics, it is absolutely slam-dunk known that the universe ends in a big freeze, not a great crunch. Perlmutter et al got the nobel prize in 2011 for discovering that the expansion of the universe is accelerating, due to an unknown effect called for now dark energy. Unless there is some future undiscovered transition, the end of the universe will be cold and lonely, as even the nearest galaxies eventually red shift to infinity.