Because they have the choice to either "double dip" or just disallow it altogether. They could easily just say "all console games are now considered software licenses; and unless a specific floating license is purchased at a much higher price (for rentals, let's say), all licenses are non transferable." It would be exactly like PC software.
But, they are forgoing said "doom" and allowing you to sell your license to authorized dealers (who would then pay a fee to reactivate said license for resale) or transfer your license to a friend with some stipulation.
Yes, it is different than what we have now. Yes, it could create a system in which all likely sales are new. And yes, it could have the effect Steam has had on the market and move more units by having sales after the initial rush of early adopters.
Now, is it likely the new CoD won't drop in price until 6+ months after release? No, because it doesn't have to. It doesn't go on sale on Steam either. People are still willing to purchase it at the original price pretty much until the new installment is announced. Will other games likely go on sale? I would assume so. The games will only bare the price the market values them at. If you don't think a game is worth $60, don't buy it at $60. Don't buy it and then complain about it.