I actually wouldn't anticipate Sony offering the 80GB model for $500 with (or without) a game in the near future ...
First off it would be seen as another price cut within 1 year which looks far more desperate than (just about) anything I have ever heard of; beyond that though, if Sony attempted to maintain 2 SKUs where the only difference was a pack-in game or two (or 5) they would find that the more expensive model did not sell that well. There is no game that has universal appeal and most gamers would not see the apeal of paying an additional $100 for Motorstorm and Resistance (and 3 other already released games).
Another way to look at this is, if Nintendo offered the Wii at $200 without Wii sports and offered a Wii with 2 controllers, 2 nunchucks and Wiisports for $250 it would probably sell alright; if Nintendo offered a Wii with 2 controllers, 2 nunchucks, Wiisports, and Zelda for $300 it would not sell well compared to the $200 model. People who see a lot of value in pack-in games (enough to pay additional money) probably already own the console and the games.
