But there will be progress because our knowledge of right and wrong behavior can never be completed. Moral philosophy is "the question of what to do next?". So people simply keep creating better and better ideas of how to be right and what to do next.
As the moral differences between people decreases then so to does the amount of problems that exists. When problems(cultural conflict) go away then that means we can focus our efforts on entirely new and better moral and cultural disagreements.