If btc down will altcoin also down or will it have a future without bitcoin
I doubt bitcoin will ever completely down, dead or abandoned, If it does, which most likely never going to happen, another altcoin will arise and take its place as the supreme coin
and all other altcoins will be traded based on this coin, and cryptoworld continue as usual
the most prominent candidates would be BCH, LTC or ETH as the next #1 crypto currency