Yeah, but the problem is you can't count it like that. Ale has no competition with the target men, who are a different category. In reality, Del Piero's concurrence are the support strikers and I'm guessing Lippi will take 3 such players at the world cup.
So you have those who were already played by Lippi in the qualifiers and the conf.cup (Rossi, Di Natale, Quagliarella...and even Iaquinta) and those who didn't play, like Totti, Cassano and Miccoli.
Now, Cassano and Miccoli won't make it, even though they both deserve it, but Totti is talking about a come back.
So, Del Piero's rivals are: Di Natale, Rossi, Quagliarella and Totti (maybe even Iaquinta). 3 of these will make it.
Personally I don't see Del Piero making it and his only chance are injuries. If two of the above mentioned get injured before the WC, then Del Piero might make it in the last minute.