Bitcoin is still the most popular crypto, I think. And I don't see reason of overthrown this gold like coin by others. Yes its price fluctuates a lot for so many reasons. But that's not all for which it would be overthrown.
I believe that there will be a new altcoin that is going to surpass the price of bitcoins someday and people will prefer investing on it, that is the reason why altcoins has also the potential to grow depending on the developers.
Never any altcoin can over come bitcoins as what ever the reason be, even if the project is good but still it is controlled by developer and when the developer stop the project development the price of the coin fells and even if the developer sell of his coin then also the coin dies.