Estimating where MBS prices might be headed has never been an easy game – and thanks to the debt crisis in Greece and a stock meltdown in China, it’s become a whole lot more difficult of late. But for now, analysts and market watchers are certain of one thing: MBS prices have been volatile the past two weeks thanks to a flight to quality, forcing investors everywhere to buy U.S. Treasuries. And because mortgages track Treasuries, yields have fallen and prices have increased. “The Greek crisis already has taken...