Technology isn't even the biggest issue - even if you had fast zero fee transactions you still have the problem of inherent volatility and deflation. Volume doesn't help with volatility here, at least not in the current designs that have fixed money supply - the incentive to hold becomes even larger the more use a coin sees - you make a contract for x coins in 10 months that's worth 10x - that just makes everything too complicated.
If someone figured out a way to peg the value of crypto to some other big currency that would have potential - but then the speculators wouldn't be making 10x.
Services like BitPay require transactions to go through quickly. If your transaction arrives an hour too late the bitcoin price in usd has changed and bitpay refunds you your money or asks you to send more money. In both cases you have to pay the transaction fee again.
I wouldn't be surprised if a high transaction fee increases the speed of deflation. Smaller transactions are stuck and will be forgotten. Spending the currency is difficult. All you can do is hold or convert to fiat.
If someone figured out a way to peg the value of crypto to some other big currency that would have potential - but then the speculators wouldn't be making 10x.