"In fact, it is not used much in the legal economy now. Yes, a rich man sells it to another rich man, but this is not the end use. Without these uses, it has no long-term future. ," Rogoff said. In other words, Bitcoin currently exists almost exclusively as a speculative tool.
So, is the Bitcoin bubble about to burst?
No. The bitcoin "bubble" has been "about to burst" since early 2011 or mid 2010. People said the same thing when it hit dollar parity - "it isn't sustainable", "it will be back below $1 shortly".
As far as "practical uses" much depends on what you are trying to practice. If you are trying to practice freedom and protecting the products of your life from then bitcoin is quite useful - among many other uses. Just because Rogoff (whoever that is) said that, it primarily indicates his/her own lack of knowledge and imagination. Perhaps he/she is just upset that he/she got in so late.
And Satoshi didn't intend bitcoin to merely be a currency, it would need to reach a point of equilibrium with fiat currencies prior to that, and Satoshi realized it.