I certainly hope they don't decide to do any more prequels set before ROTLA*. It was bad enough when they made TOD a prequel; any more encounters with supernatural/paranormal phenomena at a time when Indy's supposed to be a firm skeptic would be outright inane.
*Unless said prequels eschewed any overt, direct exposure to the supernatural/paranormal. In that case I wouldn't mind more pre-Raiders prequels.