I recently completed the main storyline. Now that I've used the dragon elder scroll, I don't think I need it. However, the game says it's still a quest item and I can't drop it, stash it in one of my 20 unused storage compartments (thanks, Hearthfire!), or sell it to a vendor (I don't think it has any value, though). I have all 3 DLC add-ons, and I'm assuming that either it's a bug, or it's part of either Dawnguard or a side quest in Dragonborn (I've already killed Miraak).