That's the part that concerns me the most. I still install (and play) lots of old games on every computer I own -- King's Quest VI, C&C: Red Alert, Worms: Armageddon, etc. And who could live without the console classics like Goldeneye or Ocarina of Time? All you have to do is pull out the disc (or cartridge), pop it in, and play.
We still don't know exactly what will happen with this new generation of games that consumers are merely "renting" from companies like EA, but piracy seems to be our only guaranteed method of preserving them. What happens if you want to play Battlefield 3 again 10 years from now? You might be able to access it IFF:
1. Your account is still in good standing (not banned)
2. EA still exists
3. EA has decided to maintain support for Origin
4. EA has decided to maintain support for Battlefield 3
5. You remember your PW or can prove to EA you're the account owner
There's not much history to base this speculation on yet, but what little we do have shows that that's an extremely unlikely scenario. If there's any chance to preserve the games we're playing now, it's probably up to us to make it happen.