Hey Duncan,
These have been discontinued for now. That isn't to say that we won't ever reprint these, it just means that we don't have any current plans to do so. The Sentinels are an old favorite. They may come back at some point in the future with minor upgrades, or maybe even as a V2. A different color maybe? Who knows? For now, hold on tight to your stash as there won't be any new Sentinels soon. In the meantime, try out something new. You might find a new favorite! If you haven't tried the Monarch yet, they are a must have. Also check out the Contraband decks. The same sorts of mysteries that the Sentinels were known for are reflected in the Contraband deck. Totally different style, but cut from the same cloth.
// L