I'm kind of glad there aren't plans for a JPIV. When I was younger I loved all three, and I can watch all three now for enjoyment, but really, the first one is the only really good one in the series. (The others aren't terrible, just not as good as the first). I really see nowhere for a fourth movie to go without feeling tacked on.
And, I must say, I think the first movie probably has the best score in any movie, ever.