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 
By 2020. So there is 4 for years even if he said that. And 4 years is a lot of time, lot of things can happen.
If we look what bitcoin made from 2011 until now its not impossible that in 2020 we will see btc much bigger and much more people will know about it.
I don't think btc will disappear ever, that sounds almost impossible.