How can you say that? They'll have less disposable income on games since they won't be able to sell them. This will effect new game sales.
You're basically saying no one who buys new games considers selling them...
For this to mean anything you have to go out and do an exhaustive study on how many people who trade games in buy new games and not just other used games.
The ratio may be extremely bias towards those who just keep the used cycle of games going.