Is there legacy content available for Hoard of the Dragon Queen and Rise of Tiamat? I'm asking honestly, as I only see Tyranny of Dragons available on Beyond. No differentiation for Curse of Strahd or Curse of Strahd Revamped either (or the Curse of Strahd reissue that came out inbetween the two).
We've already seen them reissue three 5E adventures as it is - Curse of Strahd, the combined/updated Tyranny of Dragons and the expanded-upon Phandelver and Below: The Shattered Obelisk. They have no compunction drawing on old adventures with Tales from the Yawning Portal, Ghosts of Saltmarsh and Tales from the Infinite Staircase. They've remixed old edition adventures with Tomb of Annihilation, Storm King's Thunder, Dungeon of the Mad Mage and Princes of the Apocalypse.
Perhaps one of the easiest ways to make some money for them right now would be to take the older existing 5E adventures that have been out of print for a while and have been well-liked, giving them a new coat of paint and do a couple under the hood tweaks. They've done it a dozen times in the past to different iterations of older modules like Ravenloft, Pharaoh, and the GDQ series and its worked before (even within the same edition!), I don't see why they wouldn't go for it now.