If Jagex doesn't interfere with the prices on the GE, rares will go up a bit after reaching their lowest point possible. When the rares reach a very low point, where they are very cheap. At this point, some players will decide to buy rares due to their low prices. Their demand will go up a bit, and as their demand goes up, then so does their price. As their price goes up, their demand goes down again, and the price will keep fluctuating until Jagex interferes with the GE. It'll probably not rise back to it's original price for a long time though, or not at all.