i've seen some talk of binance adding fiat pairs once they're settled in malta, though binance themselves seem to be denying it. you also have bittrex looking into dollars for corporate customers and i expect poloniex may do something with fiat when circle get their act together.
by that point there'll pretty much be no need to use bitcoin as a gateway to any other coin.
so would that make a fundamental change in how the markets interact or do you reckon they'll all still live and die together?
If altcoins are directly linked to fiat, I still think that bitcoin will influence the market movements.
Just like how ETH is already traded with USD and other fiat pairs and is mostly independent from bitcoin in terms of exchanging, but still, bitcoin's market movement strongly influence how the ETH markets move still.
As long as bitcoin continues to be the #1 crypto in terms of market cap, alts will continue to crash when BTC crashes, and go up when BTC goes up. If BTC has some sort of bear market, alts won't perform that well either. Whether or not there is a need for BTC as a medium to trade alts or not.