They way the legislation is written there is the possibility of as many as 20 possibly even 28 different varieties of cent in 2009. Since it specifies that coins struck for numismatic purposes can be struck in copper you could have these varieties.
2009 "P" zinc four designs for circulation.
2009 D zinc four designs for circulation
2009 "P" copper satin finish four designs for mint set
2009 D copper satin finish four designs for mint set
2009 S copper Proof four designs
This makes 20 varieties. But to that you could add:
2009 "P" zinc satin finish four designs for mint set
2009 D zinc satin finish four designs for mint set
Now the mint set could contain the P & D cents in either zinc or copper, or they could use both. The choice is up to the mint. I could even see the mint make and sell a 20 or 28 piece set of all of the varieties.
Another possiblity would be to have the four S mint proofs in the clad proof set made of zinc, and the four in the silver proof set made of copper. That could bring us up to 32 different varieties.
Think I should mention this to the Mint marketing dept?