I happened to be listening to an interview with him on Youtube two days ago. Pretty smart guy.

The question as you put it is very broad and may give rise to different interpretations.

If we are talking about storing value, Bitcoin is much better than fiat, as fiat constantly depreciates (it is basically a scam, and is something Salinas insisted on in the interview I saw), while Bitcoin is almost perfect for storing and transferring value.

If we are talking about replacing fiat for day-to-day payments, there are a number of question marks that remain to be seen. If it were to replace all the global transactions that are done with fiat today, all at once, it couldn't because of a scalability issue. It is assumed that little by little improvements will be implemented and with secon layers or other solutions it will be possible to cover more and more payments.