Mature altcoins are never dead.
Indeed, we have so many new coins added with premined, or hidden blocks, for pump and dump... The Bittrex thread gives some insights about what happened...
Junkcoin have none of these issues, and is mature... The price is low today, but who knows the future?
What exactly are mature alt coins? I only think 2 alt coins where successful for a long time and that was namecoin and litecoin. no other as lasting as long as them.