However, by that measure bitcoin has already achieved success. The bitcoin network currently mediates between 50 and 60 thousand transactions every day, transferring an estimated 70 million USD every day.
As far as bootstrapped nascent currency experiments go, bitcoin should certainly fulfill many criteria for "success" already.
Curioulsy the number of transactions per day and their total BTC volume have increased very little, or not at all, since September last year. So, either commercial e-payments are a small fraction of those numbers, or they are not increasing (and their USD volume is actually decreasing, since the BTC price has fallen considerably in that period).
The number of transactions increases in waves similar to the price function. Also many transactions are now being done off the blockchain. I use coinbase app on my phone and when I go to the bar in my area they use coinbase merchant. That transaction is never shown on the blockchain.