Info. on Subspecies 5 from the Subspecies Blu-ray Collection
Director/Writer Ted Nicolaou and Cast Members Anders Hove and Denice Duff talked about "Subspecies 5" in the audio commentaries and featurette included in the Subspecies Vol. 1 Blu-ray/DVD collection.
In the featurette, they said that the script was written "years ago" and it's a prequel about the origins of the vampire Radu and what drove him to become the villain in the series.
They said that it hasn't happened yet because they "want to get everything right" and give the fans "a killer sequel" waiting for the right time to do it.
At the end of the Subspecies III commentary they all expressed interest in coming back for "Subspecies 5" and Ted Nicolaou said if you want it to happen you have to "send Charlie Band a note, with like 2-3 dollars, and hopefully we can then make it happen."
So for those who want some info. on "Subspecies 5" that's what was mentioned about it. The featurette and commentaries were recorded around Oct. 2012.