Blu-Ray has a thing called BD+ on it, which lets content companies run arbitrary native code on your player (among other things). It also lets you update your player's key revocation list for HDCP. So either of these mechanisms could be used to render your old purchased content unplayable.
That's literally evil.
AACS2 allows for carrying revocation lists on discs now.
DRM stands for Digital Rights Management, but I call it Digital Restrictions Management cause that's what it is from users point of view.
The one thing I'm not 100% certain on is if HDCP revocation list updates go through BD+ or if there's a separate mechanism for those updates. However, BD+ code gets to inspect your player software and modify it, which is sufficient capability to do updates, even if they don't use it for such.
I also don't know if they continue to release updated BD+ code or if they've given up on that.
I have continuously rediscovered that files in inaccessible formats become inaccessible after time, time and time again.
They already did that for PC playback for example, revoking keys for several players.