Hard to speculate about future. We all can see that bitcoin right now is not exactly the best payment option or a currency.
BTC is better suited to be an safe haven asset, capital investment and long term option for hoarders.
Bitcoin is not doomed yet (Japan adoption!), there is still time to fix scaling problem and reach total dominance over altcoins.
But if the scaling war will continue for extended period of time, it is possible that ETH, LTC or DASH will take over BTC dominance.
Exactly, it is very hard to predict what is going to happen in next 10 year in the cryptocurrency world.
I think that LTC lately has grown up, showing it's potential thanks to the possible SegWit implementation.
But as can be observed, ETH has also a big chance to take a lot of the market ( and already has, after bitcoin ).
I also believe that Monero may have opportunity to build-up, thanks to the anonymousness of this altcoin.
After all, there is a possibility of totally new altcoin growing up, and taking big part of the market.
But all of that is just speculation about future, it is only my opinion.