People will only stop trading btc to fiat if they have to buy something exclusively with bitcoin.
Otherwise it's still more advantageous to exchange btc to fiat, as you buy anything with fiat, and with bitcoin only few goods and services.
I don't think so because I am sure people still want to have more bitcoin in many ways and trading is one of those ways. They will spend some bitcoin to trade while they still have another bitcoin to buy a few goods and service. But I don't want to use bitcoin to buy something because bitcoin is my investment now. I prefer to use fiat to buy my daily needs and save bitcoin for a long time.