Satoshi said, by 2020 bitcoin is eitheir mainstream either will disappear (quotation welcome, i didn't find it)
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 
Some people look at bitcoin as a currency, for day to day transactions... However, the way bitcoin was designed leans more toward a system for value storage + instantaneous transmission of large amounts value.
Other options will arise to perform the tasks and functions that bitcoin is unable to