Eazy, nothing says you should buy by the end of 2010. It's just that late in the model year almost always nets the best bargain prices, at the considerable cost of a lack of selection. If you've got a plan and want to stick to it by waiting to look in 2011, stick to your guns. But hopefully they'll start showing us 2011 Z's soon.
Whatever way you go, I hope you get exactly the one that makes you happy!