I've seen it handled a couple of ways around here (I am friends with several bike shop owners.. yes, I have a bike problem). Most of these guys must commit to a minimum buy and pay for it as it's delivered, so those are already sunk costs for them. Their agreements with the bike company often specify price floors on current year bikes. Their goal, obviously, is to end the year with a minimum of expensive unsold inventory.
Once it gets past that year, it varies. I know a couple of shops that have Ebay businesses selling last year's bikes. I'm not at all sure what the bike manufacturer's attitude is about this. Some will continue to discount the bikes. Some seem to hang onto them indefinitely (they might have a 2008 "new" bike on the floor, not discounted substantially).