So this obviously couldn't be pulled from the audio data of the track, but are there any plans for an Artist: get_lyrics call?
This very well could be illegal, but it would be a great feature and I'm sure finding and verifying the lyrics from across the web couldn't be too complex relative to the other Echonest functions.
You could use MusixMatch for fetching lyrics, since there is no lyrics API at the moment: http://musixmatch.com/. It's even legal, as they have properly licensed their lyrics etc. The cool thing is that echonest ids are valid identifiers when searching for lyrics: