This is how Post Credits: Makuta plots revenge of Ryan and Sunset goes in Ryan's, Thomas' and Crash's Adventures of Bionicle 3: Web of Shadows.
[At Cortex's castle, Makuta angerly walks down the halls]
Makuta: That Ryan ruined my plans to rule Metru Nui and have Sunset! I need a way to make Mata Nui gone forever!
[He sees a poster of a giant robot and Ryvine making a mask by combining the powers of the powers of the Elements of Harmony and the elemental powers]
Ryvine Sparkle: Huh? Makuta. You are free.
Makuta: Yes. And I have an idea. I'll go into Mata Nui's giant robot body and wait till he awakes.
Ryvine Sparkle: Cool. And in that Bionicle reboot, you make a forbidden mask. That's why I am making a mask that make Ryalight Glimmer more powerful then a Prime. I call it the Harmony Mask of Ultimate Power.
Makuta: I see. With this, Sunset will be mine. And you will rule Equestria. Oh. I love it. I mean. This is really classy. This is me!
[Ryvine nods and puts the unfinished mask to storage and used his magic to transfer Makuta into the heart of Mata Nui. Then the film ends with the irus out]