If you look at Coinmarketcap figures, there is a steady secular drop in bitcoin market cap as opposed to alt coins. Ether which was the main contender seems to have plateaued. There is a steady rise in other altcoin dominance.
https://coinmarketcap.com/charts/Now total market capitalization peaked at 800 billion sometime in Jan. This has dropped to approx 500 billion since. In December Bitcoin briefly reached 60 percent in market dominance. I think it was due to the influx of new players who joined due to the hype.After a quick drop we are seeing Bitcoin drop to around 34 percent of the market. Now the question is whether this will further drop. If it will drop who will be the new contenders. In all likelihood we will have a slew of new small currencies replacing the giant Bitcoin, each with a market cap of around 3- 4 percent. But that will mean that Ether and perhaps Ripple will be less important. I am not saying the price of either will go down, but that they will be less dominant in the whole market.
Any coin can change the top currencies, but would they? I can't tell anything about bitcoin, but coin such a ethereum and ripple, has build their framework for pretty long time, and shows stabile growth (if not counting pump in Dec-Jan 2018). So if some project will be so useful and powerful as those guys, it will bit them, but you can't know and can't tell for sure.
