There is no way I could buy a 2010 Camaro SS knowing that a supercharged 568hp Z28 could be coming. If you really like the Camaro, I would just wait for that. If you want something now, I'd go with and 08 or 09 GT500 below msrp.
I wouldn't hold my breath waiting for that one, especially considering the financial shape that GM is in (and the fact that it's quickly becoming a ward of the state).