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
I also doubt the bitcoin will totally fall, die, and be abandoned. Well, there is nothing impossible in this world, and if it does happen, it is a real sign of the failure of bitcoin developers to compete with other altcoins and of course, its role as the ultimate and most dominant cryptocurrency of all will be taken over by altcoins that deserve the title.