Cajun country residents threatened by Mississippi River flooding were packing their things Friday as they anxiously awaited word on when federal engineers could open a massive spillway that would inundate hundreds of thousands of rural acres and swamp thousands of homes. The Army Corps of Engineers is close to opening the key Morganza floodway to relieve pressure on the levees downstream that protect the more densely populated Baton Rouge and New Orleans areas. The corps could make the move as early as this weekend, though officials stress that no final decision has been made.