I think it's time for a Legal Deposit scheme for Games.

- Game publishers would put their games in Escrow when they publish.  
- Game Services could publish a spec on how to interpret the game contents.
- 'Orphan' games would actually be preserved.- Users that purchased the Game would then be entitled to a copy of the escrowed item, plus the design on how to run them.

This, combined with an export of user-generated data would allow for usability after Stadia or the Game Publisher sunsets the service/game.

And to be honest I'd love to see this extended to all Online "Stores" that don't let you export usable contents.

Barring that Game Services could enter a Ulysses Pact with users if they are serious about the long-haul.. 

 For each purchase a user makes put 10x in a locked escrow fund.  When the service cancels that money can be used to migrate the games to a new provider or payout back the user.

- If a Game Service gets few users it's not a lot of money to exit and actually would increase satisfaction.
- If a Game Service does get popular then there's an explicit feedback loop that reinforces the durability of the system and alignment of interests.

Evernote announced something like this, but never really followed through.   A small company called Forever actually does have a preservation fund that is purpose driven.