Several $1 billion-plus mortgage servicing packages have reached the auction market the past few weeks as sellers try to complete deals before yearend. But one potential obstacle could gum up the works: a continuing decline in interest rates. With the yield on the benchmark 10-year Treasury hovering just above the 2.0 percent mark, mortgage rates are now at their lowest levels since the spring. And as any servicing investor knows: A declining interest rate environment is never a good thing to sell into. In early September, U.S. Trading LLC, Cherry Hill, NJ, hit...