Sure you will. Maybe not as much, but it will still be there. There are still illegal marijuana dealers in legalized states.

Women will continue to be 'streetwalkers', because they can't access the regulated place of business - maybe because of previous bad behavior such as stealing or assaulting clients - maybe because they have a STD and the regulated place won't let them work for health reasons - maybe because they are being forced to do 'overtime' after their regulated job by a pimp.

Men will likewise continue to use streetwalkers - maybe because they just like them better, maybe because they think their partners have less of a chance of finding out if they pick someone up in the street vs paying with a credit card on an app - maybe because they have been abusive in the past with regulated prostitutes and have been banned - maybe because they want to save 10% on the price.

Or they are part-timers that only do it once in awhile.

Prostitutes have been on the Internet forever. Legal or not, streetwalkers will continue to exist. The problems, real or perceived, that streetwalkers cause in the neighborhoods they work will continue to exist.