So, I had a flash of inspiration earlier today, and I gained a sudden realization of where this story could be going, and what may happen over the next several seasons. I'll list my thoughts here, so let's see how it goes.
Season 3 had us end with Ruby, Jaune, Nora, and Ren heading for Haven Academy, located in Mistral. Season 4 will cover the trip to Mistral, followed by the team's investigations in the academy and kingdom. Within they will encounter some of the fallout from the Battle of Beacon, including the paranoia and mistrust, and will discover that someone is working to perpetuate that. They will work to defeat this villain, and may either succeed or fail. Either way, they discover clues that lead further in their investigation, pointing them to Atlas.
Season 5 will have them arriving in Atlas, wherin Ruby once again meets up with Weiss. Thanks to mistrust towards Atlas, there may have been actions taken to prevent entry due to others seeing them as having done wrong, leading Ironwood to adapt a very defensive and isolated period of time. Ruby will find her way in, however, and discover another villain there, this one working with the White Fang to try to sabotage Atlas' military further. Though they attack the villain, he or she manages to escape when the White Fang perform a major offensive, managing to attack not only Atlas, but also decimating the Schnee estate or company. In this attack, Winter will die. Weiss' father may be devastated, but Weiss shall leave her father's grip, and join Ruby... provided Ruby helps her take vengence on the White Fang. Thus, since the White Fang have been allied with the big bad in the past, the two follow their lead to where the White Fang is stationed... in Vacuo.
Season 6 will have the team arrive in Vacuo. Here they will hunt the White Fang, and in their hunt will find Blake, who had run there to both remain distant from her friends, and try to find a way to deal with Adam once and for all. Together they will do just that, although Blake will likely try to do it on her own to save her friends. In the end they will fight Adam, Blake and Weiss likely attacking him together, and either Blake will kill Adam, or Weiss will capture him, to be taken into Atlas custody. Either way, after their investigations here, their trials lead them back to Vale, to get back on the trail to find whoever is behind the disasters occurring everywhere. Blake, with Adam finally dealt with, will rejoin the team.
Season 7 will have the team's return to Vale. Here they will investigate further, and eventually find Yang... who is either drunk, searching for her mother again, or fighting the Grimm in Beacon. Through their investigations, they find the tower and the grimm still frozen... but no sign of Cinder. Deep below however, they may find a clue to what happened to Ozpin at last. With few other options, they will follow this clue to seek Ozpin. Yang will rejoin them at this point.
Season 8 will be split... half of it will be the now-reformed Team RWBY seeking out Ozpin's hiding place, while the other half will be brief detour stories, showing the other teams dealing with the disasters happening in other kingdoms, as things are getting worse and worse. In the end they will find Ozpin, and learn about Salem and where she is, as well as hints of her grant plan.
Season 9 will be RWBY's quest to reach Salem and stop her plan. It will be quite a quest, going through a lot of grimm, but eventually they find Salem and learn her plan.... The Maidens.
Throughout all of this, the other maidens will be discovered, and either killed or captured. Salem's grand plan has been to cause enough chaos that the maidens come out of hiding, so that she can take ALL their power AT ONCE, thus making her a god. The team may even encounter Salem, just as she kills all those who have the power of the Maidens within them... in my opinion, Cinder, Emerald (Stealing the power of spring), Neo (Stealing the power of Winter), and the Summer Maiden (Captured). Having gained the power of all four seasons, Salem and RWBY would of course fight in a final climactic battle, that may end with team RWBY killing Salem, and the four members gaining the power of the Maidens themselves.
Other notes unrelated to specific seasons...
Each season will have a specific villain that the team will need to deal with... a minion of Salem that was introduced previously. Emerald, Mercury, Neo, and Adam will appear to be the ones pulling the strings in each region. Adam in Vacuo, with the other three I am unsure where.
The remaining three maidens will be revealed in each of the lands, only to end up either captured or killed. Possible that Neo will kill the Winter Maiden in Mistral, Emerald will kill the Spring Maiden in Atlas, and the Summer Maiden may appear in Vacuo and survive, only to be captured later.
Members of the other teams will be discovered in their respective kingdoms. Sun may appear in Vacuo to help out with the White Fang, and Penny may be rebuilt in Atlas and assist in that season. I am unsure which teams are in which regions outside of that.
Ironwood and Qrow may die at some point. Possible, but not definite.
I am unsure as to how Team JNR will factor into this... they may leave at some point, or stay through a good portion of it.
Right, that's all the thoughts I had.... the basic ideas around the structure of the seasons struck me like a bolt of lightning, and then the rest of it just naturally filled it out. The idea and structure came to me by thinking of it as a video game... the first three seasons were the whole tutorial area leading to the "burning of the hometown", which became an investigation to stop the Great Evil while Bringing Together The Party.
Do let me know what you all think.