The universe will end. There might be more universes
The universe will end one day, either from heat death, great rip, etc. These are just theories on how the universe might end. Just like the idea of more than one universe, depending on what theories you believe in (ex: many-worlds theory). There might be a multiverse with an infinite or finite number of universes, we just don't know. Perhaps when the universe ends a second Big Bang will occur and a new universe will form, but we just don't know what will happen.