I agree with the above statements. If you want to learn the piano and develop a seriously good technique, just playing pop music will only get you so far (and not very far). You'll know a lot of chords, and some pretty simple melodies (without having to worry about a lot of key/time changes).
Taking classical lessons will help with your development, but it's very easy to get caught up in JUST classical music, and totally forget about other music that you enjoyed before hand. A lot of rock/pop musicians will associate classical music with 'calm' music or 'boring, old', just as a lot of classical musicians will associate rock music with 'boring, simple, noise'. To each their own, but if you have a classical background, you start appreciating the smaller details in rock/pop/blues that you may have not noticed before.
I'm a huge Soundgarden fan, and sometimes I'll catch this really awesome melodic line, or hear some secondary dominant chords (i don't even know if they are aware of it in the theoretical sense, but they know it sounds good!). My friends will just hear it as "that cool riff". Meh.