While I understand that there's some common sense lacking from the new Polymorph rules in 3.5, the bottom line is that those who don't apply common sense in the absence of its written form are those who are slaves to the letter of the law, and those who have no real concept of the spirit of the law. This is what's most important, at least to me, as both a player and a Dungeon Master. What does the spell description specifically say vs. what was the likely intent of the designers?
Monte Cook, in his preview of 3.5, confirmed a lot of the things I suspected as it pertained to the 3.0 books and why some of the spells and other things were written the way they were, so I'm reasonably pleased that my rulings as a Dungeon Master on the side of "likely intent" from the designers lined up, generally speaking, with the intent of at least one of those designers.
You might perhaps not gain the elemental subtype by the letter of the rules, but it seems most likely to me that in wildshaping into an elemental, and gaining all its extraordinary, supernatural and spell-like abilities, the only thing you'd be lacking is type, and as others have noted, it just makes no sense for an earth elemental to have the internal organs of a PHB race Druid (or any other mortal race, for that matter), and thus be vulnerable to things like a Rogue's Sneak Attack, critical hits, etc. If you wildshape into an animal, then you have the animal's type. It references, for rules consistency, the Polymorph spell for the wildshaping ability; at 16th level and above, a Druid can wildshape into an elemental, and since it uses the term "wildshape", it must then conform to all rulings of regular wildshaping, with the exceptions noted in the specific ability description (i.e., the separate usage-tracking for elemental wildshaping, the acquisition of spell-like abilities of an elemental, etc.). In other words, if a Druid is wildshaping into an elemental, then by the nature of wildshape, which references Polymorph, which references Alter Self, you gain the type of the creature whose form you're taking.
Does anyone for an instant think that a Druid using the "Dragon Wildshape" feat from the Draconomicon doesn't gain the dragon type when they shift? Some things you just have to apply common sense to, and throw rules lawyers who are whining to the contrary (likely just because they didn't think of it first, and don't want it used against them) out the door.
When in doubt, err on the side of fun.
