"While the qualification revisions will impact Medallion members in different ways, Delta expects the total number of Medallion members to remain about the same, with slightly more members moving up in status. (emphasis added)"

My take on this is that it is 100% true. Think about it for a second. With the Skymiles elite qualifacation program staying more or less the same up until now, not many people moved up their status every year. But now, most of the high-fare pax will be moving up, which will be more than before. It doesn't matter if three times as many don't bother to or can't requalify or they get demoted a level.