Scientists generally say that our sun is a white dwarf and it is estimated that white dwarfs live approximately ten billion years. Our sun is about five billion years old so that leaves about five billion years left. It is estimated that the sun has used up about half of its hydrogen.
The older the sun gets the more it expands. It continues to run out of hydrogen and helium and as this happens the sun loses its brightness. The outer layers of the sun (after many phases) will begin to drift away and form a planetary nebula. All that is left is the core. It shrinks and cools and becomes much much smaller.
When all of this is said and done it will then be called a black dwarf which is another saying for dead star.