I don't think it's the end of the line for bitcoin, because it's true that 2018 has been a low year for BTC, but when you look at coinmarketcap.com you can see that bitcoin has 53.3% of the total market, although its overall value has decreased, its share share has increased, which says that the rest of Altcoins still have to work hard to hope that one day they can displace bitcoin.