The episode will mainly cover Cyberfun Tech and it's animatronics based on the teaser videos and images. however, Martin stated in a QnA that 4 will cover an "Interesting" part of the story

This episode will be really different from the previous 3 episodes and other analog horror series for it is going to have more "cinematic" scenes similar to the live action segments seen in the Mandela Catalogue 4.

The animatronic characters will be slightly redesigned to stay further from Five Nights at Freddy's. With bon having a white collar and animal print bowtie as well as a baggier suit rather than the bulky costumes the fnaf characters have, Boozoo also has a baggy suit, Sha's proportions being less defined, and Banny remains the same. Billy's new design is unknown

Unfortunately, Sophie and Jenny won't be appearing in 4 confirmed by Martin.

Once it releases 4 will be the longest episode in the series for now, being over an hour long.

In a recent update from martin, he said that 4 was originally gonna be released this month but decided against it due to the episode looking rushed and the FNaF movie coming out next week. So expect something special coming out in November.

That's basically it.

Some more stuff in the Replies