okay i know i am gonna get flamed for this but i'm gonna go ahead...
when I was in college, one of my instructors played us a CD that a buddy of his did.
apparently this buddy is some sort of mad scientist type who had a way to remove just about anything from a stereo mix.
the CD had a Stones song, i think it was jumpin jack flash or something. there were three different mixes: no vocals, vocals panned hard right and vocals panned hard left.
and supposedly he did this all from the original mix of the song without access to any multitrack masters!
he also said the guy took another stones song and took the distortion off the guitar!!!
i know this sounds like pure witchcraft or you guys might think i'm an idiot, but the instructor was a major recording engineer that has done some world famous stuff, so i doubt he was just trying to fool us.
will any consumer technology be able to do this for a while? i don't think so