Let's define some definitions WRT a new paradigm as it pertains to Apple's iTunes store:
High Definition: Whether it be D/L's or streaming, high definition will not exceed 1024 kbps. More likely double the current offering of 256kbps to 512. With VBR, we're talking 312 or thereabouts. Still a far cry from 16/44.1 (1411 Kbps), let alone any anything higher.
Low Definition: does it matter?
Remember this: high def as it pertains to downloads (forget streaming) cannot exceed a particular price point which is defined by the average consumers internet connection.
Don't get me wrong. I'll be the first to gladly eat crow.