What is the difference in the way Winston and Julia appear to view the future in Part 2, Chapter 3 of 1984.

I would summarize the difference between their respective views of the future with this quote:

She was very young, he thought, she still expected something from life.

As this says, Julia seems optimistic.  She thinks that her life has meaning and is important.  She seems to believe that she can win -- she can beat the Party.  We see this in her behavior at the end of the chapter -- the chapter ends with her making plans for the next meeting between the two of them.

By contrast, Winston is deeply pessimistic.  He says that they are already dead and that the only way to think of yourself once you've started to fight the Party, is as a corpse.

So, Julia expects something from the future, Winston figures he's already dead.