I am not familiar with Joseph Parker, but it looks like he did great in his last three fights. But despite that, I don't think he'll be able to beat Usyk. In Usyk's rematch with Dubois this July 19, he showed how dominant he can be in his fight. I have no doubt Usyk will outbox Joseph if they fought.
We can't be too sure about this till the fight happens only then can we find out if Joseph parker can beat Usyk or not. Am a big supporter of Usyk, but I also understand that Usyk cannot be champion forever. At some point he's going to lose unless he retire before then. Joseph parker has been winning his recent matches same as Usyk so you can't completely write off Parker. Parker is also showing some similarities that Usyk was showing back then when he was rising to stardom. Usyk Vs Parker would have been more interesting than what we saw against Dubios.
I voted for Usyk to beat Parker. We've seen Usyk's speed against Dubois and so even if in paper it looks like Parker might have a good chance, it might be another easy fight for Usyk here. And if he beat's Parker, then he swept this division for good. Parker's previous opponent doesn't have the boxing IQ of Usyk. They all have the mentality to brawl and uses their power but Parker is too smart with that. However, with Usyk style of a southpaw and being slick, it's going to be very hard for Parker to just play defense early and then wait for his opponent to get's tired. And so if he goes early and fight toe to toe with Usyk, he might end up like Dubois and gets knockout by Usyk.