I wouldn't say that Bitcoin will fall, I just think it will get surpassed by another cryptocurrency. At the moment it takes about an hour and $10 in fees if you're making payment. Of course it gets faster if you're paying higher fees but that is not going to work for everyday payments in shops and etc.
I think BTC is worth more than other cryptos because it was first of its kind and eventually it will get surpassed by other technologically more advanced crypto. Will BTC retain its value - yes but it won't be the most valuable crypto. Anyways that's just my opinion so take it with the grain of salt.