As others have already stated, there tends to be a lot of "This could happen" doomsday predictions, but I have never seen any of those actually happen. When you buy something, it's still there even if Apple stops selling it.
Yeah, much more likely for a disc to rot/go bad than that... although there's the very remote chance that Apple someday decides this bizz is just not big/profitable enough for them and they sell it off or completely terminate it (and probably offer at least partial refund to minimize the backlash).
The more likely real issue is the content could get altered/"upgraded" in undesirable ways instead, including having stuff like HDR10/DV/Atmos dropped (probably temporarily) or Paramount's (ahem) "upgrades" to their latest "immaculate" master/transfer, LOL...
Basically, if something's important enough to you (and you're very particular about the PQ/AQ... or in this case, potential reediting for censorship), then make sure you have a good disc of whatever as well and not rely solely on the digital...
_Man_