It's not been explicitly confirmed but presumably, yes, the additional tiers of Accursed Hoard sacks will come from floors 51-200. As for what they contain we still have no idea. There are a few minions and mounts that are, as yet, unaccounted for. Some of those might be in the bags. They might simply have the same loot with higher odds of a rare drop though. We'll get a clearer picture from the patch notes I expect.