The nature of the third collaboration is vaguer than the previous two. It features a new Steins;Gate chapter title-esque image, as well as a new divergence number which has not been previously explored. However, the project’s page notes that further information will be made available later.

UPDATE (February 28, 2020): New details on the nature of the sixth project have been made available on its website. Notably, it will involve a crossover between the characters of Steins;Gate and characters created by the Japanese company Sanrio, which includes the world-famous Hello Kitty. This crossover will take place on the aforementioned unexplored worldline, 0.549111%.

The announcement tweet notes that further details on this crossover are currently forthcoming.