Old IP is becoming a lucrative and very cheap revenue stream for a lot of publishers now. All of a sudden those 10 or 20 year old games they didn't care about have value again.
Considering also how most publishers and devs view the pre-owned market I don't think it will be long before everything comes with a server related killswitch or requires an account purchase per game for second hand installers forcing people buying pre-owned titles to register and pay for an account before the game will play.
Fast forward 10 or 15 years and it seems likely physical media will be a thing of the past anyway, effectively ending any future for older games or a pre-owned market.
We've always been sold a limited licence rather than exclusive rights where the actual software is concerned but the industry could never control that when they're putting the physical media in the hands of the consumer. When the publisher also retains control and ownership of the media games are delivered on, we're pretty much f**ked in terms of long term or transferrable ownership.
Nice to see GOG is still alive but there's definitely a gentle but concerted and accelerating push to take control of things we buy away from us and handing it back to the publishers.