First of all depenalization is different than legalization, to own few grams of marijuana is no longer a crime yet its not legal to sell few grams of it.
Regarding the topic, I disagree with those who say that legal prostitution would have no impact on the dating market.
First of all, all the guys horny and looking for sex (not validation or companionship) would no longer hit clubs and pubs therefore changing the M : F ratio in those place, they would no longer chase women aggresively in those place giving them the illusion of being in demand as people.
Average guys unable to get decent feedbacks from women would probably appreciate the safety and easyness of getting fast and CHEAP sure sex, they would no longer obsess on chats or social media but would take the fast way.
These facts wouldnt make much difference for top %nters that easily get women while it would change dinamics between the average men and the average women.
After a certain point the average guy would drop the average girl if too much drama comes and not enough sex balances it, we would observe a recalibration in the attention vs sex negotiation between the sexes in the average group.
So that would make a difference for the average man for sure, an average woman that has nothing else than sex to offer to a guy would be forced to add something to the package, add something in terms of quality or remove some discomfort in terms of drama and demands.
Men are pragmatic creatures and at some point consider the cost-benefit ratio of things, think of the mgtow epidemic we see recently.
The real deal breaker would be social acceptance and lack of social shaming for both clients and professionals, in that case word of mouth would push even more men to consider and different behaviour.
Escorts dont provide companionship or validation but allow fast, cheap and sure sexual release especially to older men.
Your post has just given me a brain wave. With all of this modern say 3rd wave Feminism that supposedly champions the ability for women to choose, is it not possible that by this very definition that it is the 3rd wave SJW Feminazis that could be the ones to get this legislated either directly or indirectly and therefor bring about the conclusion that you have stated? Wouldn't it be ironic if this was the case?