But how can it be mainstream with 7 transaction per second ? And if it's not mainstream, satoshi's logic woul tell us that bitcoin will disappear by 2020 
He also designed the original code to be modular and easily upgradeable. The current limit on upgrading block sizes (to increase the transaction / second output) is dependent on the block size increase debate that is going on. I guess he didn't foresee all the politics of this!