When UB and I have been writing out Part IV script, we've made it a point to keep the references to the old movies to a minimum. If a Part IV is going to work, it's going to need to work by itself. While Parts II and III did have references to the movies before, they had original villains and they limited references to earlier movies and more importantly, they told a good story and worked on their own.

Now you can reference the older movies, and use them in any new story, but be careful because you could just end up recycling what we've already seen before.