Why season 6 won't, and shouldn't take place before the movie:
- It has been stated multiple times that from now on (and by that, i mean after the movie) the series will take a different direction. Zach Callison himself said on a interview that he knows "an insane amount about what's coming up", and that "it's all so great." Ian has said that we shouldn't wait for more of this show, and by that he meant "Steven Universe as it was until now", also stating that "there's going to be more, but it's going to be different, and it's going to be something new". Finally, Rebecca has mentioned on an interview about the movie that "what's gone on in the series and in the film will matter in the future " (you know, more Spinel). The article for Season 6 has several evidence on that, you can just look it up.
- There's a new VA, Johnny Hawkes. Dunno if that counts as evidence, but...
- "Young'dult" Steven is great, we need more of him. And i doubt the Crewniverse would make such a dumb move by choosing the status-quo over a myriad of new possibilities.
- And most importantly, they just can't keep destroying Zach Callison's vocal chords by forcing him to sound like a little kid, lol.