I think it's too early to say for sure. I'm pretty sure they just want to finish Rohan's stories first. It's logical to finish Rohan's stories before going to Dead Man's Questions and then going to Part 5's stuff. That said, I just looked it up and Rohan and Dead Man are based on one shots, extra manga content. While PHF is based on a light novel. Different mediums have a different likelihood to become reality. Guess we'll see, but again first Rohan.
ALSO, I just noticed The Run is a Rohan story from 2018 so perhaps this will be the last Rohan ova and they've just been choosing the fan favorite stories up to now. Or maybe they are trying to appeal to long time manga fans that are keeping up with Jojo's current Part.