Yeah, they technically don't need the MC for completing it but I'm sure that he will be integral to the list completion.Technically I think Josy could have sex with a guy instead, since she and Maya are completing the list together now. They could have an all girl threesome, too.
I doubt Josy would have sex with a non-MC guy either, but it is more likely than Maya doing so.
Argh, I want part 5 to be here sooner!