no it won't help with adoption at all, people aren't going to adopt cryptocurrencies just because a random altcoin exchange, no matter how big, started accepting fiat for day tradings! and this is only a step in right direction to make his business even bigger and run a bigger monopoly in altcoin trading business and push other smaller exchanges that may even be better out of the game! and this kind of centralization is very dangerous in this market. it simply gives them too much power to manipulate the altcoin market as they see fit.