I also think that knowing that the games can't be traded in will cause people to be more selective about which games they buy... why spend $60 on a game that you might not like and you can't trade in at all to recoup at least some of that cost.
This might lead to prices on new games dropping faster just so they can move software. So if you are the sort of person willing to wait a few months for a game you might benefit by waiting for the price to drop.
I don't trade in games personally, but I also usually wait for the price to drop or choose from used games. Right now the only game I think I would buy immediately at full price would be a new Mass Effect game.