John Russell has announced that Akinori Iwamura will head to the bench and that Neil Walker will receive the majority of playing time at second base. Walker has already received plenty of playing time since his callup because Andy LaRoche has been unavailable; this announcement means that Walker will continue to receive playing time.
That's a good thing, not only because the Pirates should try to learn as much as they can about Walker before Pedro Alvarez's arrival complicates things, but because removing Iwamura is a case of addition by subtraction. Iwamura showed up in camp heavier and slower than usual, and he can no longer hit or field. I don't think there's a Pirate fan out there who would miss him if he were cut entirely.
Walker hit brilliantly this year at Class AAA Indianapolis and has continued to hit since arriving in the majors days ago. Second base isn't his natural position, but he should be an obvious upgrade over Iwamura.