What will you do when your parents are gone?

I have often wondered what affect the loss of my parents will have on my life.  I talk to one or both of them every day, but only see them at the most weekly.  I look at my mother who has lost both parents and is the only surviving sibling and wonder what her life must be like.  I am not dependent on my parents or my sister, but the knowledge  that they are there gives me emotional and psychological support.  I know I can pick up the phone and talk to any of the three.  What would I do if that was not an option?