It's Mario Kart, there's nothing to sell.
Don't want it? Don't get it.
Want it? Get it.
If it's anything like Mario Kart Wii it'll be sold out constantly for 6+ months. So by pre-ordering you're saving yourself the hassle if you do change your mind.
3rd Party Wall of Shame
http://www.nintendoworldreport.com/forums/index.php?topic=30478.msg581036#msg581036