In a recent interview with Onion's AV Club, Bruce pretty much puts his foot down and explains why he has no desire to do a fourth film anymore.
From Onion AV Club:
AVC: In your opinion, is Ash worthy of more movies?
BC: No. I think there should be an end to everything. I mean, did anyone really want
Indiana Jones 4? The answer is no.
I've taken a poll in about seven theaters now. Of 300 people, three hands go up.
You are bound to disappoint. I would rather disappoint with a brand new original movie. People worship
Army Of Darkness, and God bless them for it. It's a beautiful thing. The movie bombed when it came out, and not many people are aware of that. Twenty years later, the thing has picked up speed, and it's on American Movie Classics now. That was a long time ago, and whatever we do next will always be compared to
Army Of Darkness, and I don't see how we can win.
You make that movie, and I can tell you the quote right now, "Oh, it's not quite as good as
Army Of Darkness." Then we would have gone through immense physical pain and anguish to bring something out that ultimately disappointed. That's really not what I'm into these days.
Bummer, but he's 100% right. Let it be.
http://www.avclub.com/articles/bruce-campbell,23651/