As of now bitcoin are raising its value due to pandemic the demand for fiat currencies have been decreased drastically and digital currencies are now in demand. This may lead for another price raised on btc so i may say as of now its better to invest on bitcoin while its still low.
As for the fall in demand for Fiat currencies, it sounds quite original, because with all due respect to cryptocurrencies and bitcoins in particular, but all economic activities, payment of taxes,payment of utility bills, and finally wages and pensions require the mandatory use of Fiat currencies, and this state of Affairs will continue for a very long time. Therefore, the fall in demand for Fiat currency in the current pandemic time is not expected. Another issue is that when economic activity slows down, the released money requires a new sphere of application and bitcoin is perfectly suitable as an investment object.