I don't think we have to worry about that for a very long time, but Gord O. alias "The Professor", has this to say about your question.

Actually, some scientists believe that the universe will never end. Some scientists believe that the universe is now expanding because of the "Big Bang", (ask Sean Oderkirk to show you his answer about a similar question), and that it will eventually collapse inot a "Big Crunch".

After that, another "Big Bang" and another universe, is possible. Other scientists believe that the universe is continually making new universes and will go on forever. Still other scientists believe that the universe will just continue expanding forever.

The Hubble Telescope is helping to determine which of the theories is most probable. One of the things that scientists need to find out is how much mass is in the universe. Can you imagine trying to guess how much all the stars and planets weigh!!

There is no answer to your question...yet.