Not necessarily. That's just one of the theories of how the universe will end. There's one theory similar to the Big Rip which states that the galaxies at the edge of the universe will eventually reach the speed of light and will disappear from our observable horizon. At the speed of light, the activity of those galaxies will freeze and time will stop for anyone or anything in it. For all practical purpose, those galaxies will have turned into light.
Using the ideas from Roger Penrose, it is possible that the universe will once again explode into another Big Bang eons after all of the universe have gained the speed of light or have turned into light. https://cosmosmagazine.com/space/universe-slowly-fading-away https://cosmosmagazine.com/space/universe-slowly-fading-away
