The dominance figure doesn't represent what you mentioned in the video. BTC is the gateway from FIAT into crypto. This gate will be the primary reason why BTC will hold its value, at least until more Alt-Coins get accepted at exchanges for FIAT to Crypto.
Presently the Fee structure around BTC is severely hindering small investors; which is why ETH has been pumped somewhat. The only real risk to BTC dominance as I see it is ETH since it's one of the only other cryptos where ppl are allowed to exchange for FIAT.
I think overtime this will change; I wouldn't be surprised to see Ripple get mass adoptions given that it's currently supported by big banks.
Is it possible BTC gets dethroned? Maybe; but not in 2018. Will the whole crypto bubble pop? Absolutely not. All capital inflows would need to stop and currently there is 0 sign of that happening, if anything it's increasing.
Crypto is a market just like any other with Supply and Demand. Crypto Supply is limited by design; and with more capital coming every day that will only cause the price to rise which is what we are seeing now.
When my dad (who is 60 and has never touched a PC in his life) asks me about what BitCoin is... that says something. He asked me how to buy a few thousand dollars worth.
The problem with this assessment is that while many crypto investors might jump into ETH before BTC to send between exchanges, they quickly move it to BTC to buy their favorite altcoin. BTC is also what they move it to when they sell that altcoin. The fees in an exchange are separate from the fees of the actual blockchain, hence why this occurs.
I've mostly used Bittrex/HitBTC and they have ETH pairs for almost everything; i cant say more for about any other exchange.