Let the speculation begin! It may not be a sign of an iPhone refresh, but we've received multiple tips today about an imminent price drop for Apple's flagship smartphone. According to a pair of trusty tipsters, Radio Shack is prepping to cut the cost of AT&T's 16GB iPhone 4 to $169.99, with a two-year contract, from $199.99. The 32GB version will likewise take a $30 plunge at the Shack, ringing in at $269.99, and the price of the 8GB 3GS will drop to $19.99. Phone Arena is likewise reporting on Target slicing up the old Apple price tag, but lists varying numbers based on carrier. If all this talk turns out to be true, those prices should be ripe for the picking starting tomorrow.