Depends on the stage of communism. In a low stage communist society (as well as late dictatorship of the proletariat, 'socialist' society) it would likely exist at least in some form. Hopefully this form will be less coercive. This stage is likely the best any of us could hope to see, which is why it is important to recognise sex work as socially necessary work.

In an advanced stage, "From each according to his ability, to each according to his needs" society prostitution would likely not exist, at least as we currently recognise it. There would still be a need for porn, but it might be produced more as a hobby, as the line between hobby and creative work would be blurred.

Or what do I know, maybe people will just be jerking it to Karl Marx hentai.