I think all the formats you mentioned above wasn't conceived as "cd killers"; contrarily, they were intended to be differents "alternatives" to choice from.
Mini-Disc: with it you can record and erase your own music, compress it, etc.
DVD-Music: I don't know said format, but if you wanted to say "DVD-Audio", such format was intended primarily to "audiophiles", so that was and is their "target".
SACD: again a "audiophiles" oriented format.
HDCD: This was an "enhanced" cd, which included 4 additional bits more than the normal 16 bits cd; moreover, they are compatible with normal cd players too.