Bitcoin's current market cap is above 66% of that for all the other altcoins combined. Even if it went down to, say, 40%, BTC still would remain dominant in regards to market capitalization. Bitcoin is the most trusted coin among crypto currencies, and, in fact, all the other alts owe BTC that they are getting any adoption at all. Can any of them replace the king? Maybe, but not in this universe, where, apart from being number one already, Bitcoin has the best team of developers around.