Steam handles this much better. If a game is removed from sale for some reason people who already purchased it still have access. For example, I still have access to the original Prey even though it's no longer available.
I purchased the original version Deus Ex: Human Revolution on the Steam store. A year or so later, they released the "Director's Cut" of DE:HR. Steam automatically "upgraded" my copy, so now I have the Director's Cut version in my Steam library.