The fourth reveal in the Platinum 4 series ended up being an April Fools' Day joke, which rubbed quite a few people the wrong way. Waiting weeks and weeks to find out the 4th reveal was a joke was quite a bit disappointing. Turns out there was more to that joke than we originally thought.
Platinum is now teasing a fifth reveal in the Platinum 4 series. They're calling this a 'Bonus Stage' announcement, and apparently details are coming soon. To coincide with this reveal, a fifth star titled “????? – XX.XX.2020” has been added to the Platinum 4 website.