I think I've got some of the background of RWBY figured out. I'm just trying to get those out before volume 5 comes out, so I can say I called it if any of my predictions actually happen in the show!
Disclaimer: This post contains spoilers! Do only read if you're caught up with the show(End of Volume4)!
Like many people I also think Ozpin is the reincarnation of the wizard from the maiden's story.
But I also believe that in one of his former lifes he was the king of Vale who is also Jaune's great great grandfather. Why does no one know that Jaune is related to the former king? That's because he stopped being a king after the great war. I believe he changed his name and married a woman who did not know who he was. He never told her or their children and all male heirs of the family became strong huntsmen. After the king died and the wizzard was reincarnated in someone else, the sword was kept in the Arc family and passed down from father to son for four generations until it came into Jaunes possession. This sword is also the "Relic of Destruction"! I don't have any proof for this one. It's just a gut feeling, but it would fit the other relics that I think I have discovered!
I think that Ozpins cane either is or hosts the "Relic of Knowledge" and it works in a way that the soul and memories of the wizard are on death transfered to a new host so he gets wiser with each reincarnation. The cane then always finds a way to the new wizard!
Why do I think the cane is a relic? Simple, I expect Cinder to have burned Ozpins body completely after she killed him, like she did with Pyrrha. That's why nobody could find his body and all said he was missing, but Qrow found his cane. It must be something very powerful to be able to resist such a destructive force that can completely disintegrate metal armor pieces! Which brings me to my next theory.
Pyrrhas headpiece is also one of the four relics! Cinder disintegrated not only her body, but also her armor. Almost everything turned to dust, not only the leather parts, the metal arm and leg pieces, too! The only thing that wasn't destroyed is her headpiece falling to the ground. I feel that Rooster Teeth have shown us this little detail has some sort of meaning. They wouldn't do it like that if it meant nothing. Many times before small details that looked unimportant have shown to become important at a later point of the story and the people who caught those details when they were shown always kinda knew some of the things that were coming. However I believe that her headpiece will turn out later to be the "Relic of Choice". Why that one? Simply because her last days on Remnant were all about choice and I think Rooster Teeth would follow that symbolism!
The last relic, the "Relic of Creation" I don't have any clue what it looks like at this moment, but I believe that Salem has it(or will get it in the near future with the help of Professor Lionheart) and used(or will use) it to create new, more terrifying species of Grimm.
Now this is what I think will happen in future volumes:
Volume 5 will be for the most part getting team RWBY back together. At the end of volume 5 and throughout volume 6 Ruby and her friends prepare for a big attack on Haven that will never come. Because Salem gets the relic that was there without any fight and instead her allies prepare to attack either Shade in Vacuo or Atlas. While in Mistral Ruby tries to learn how to control her Silver Eyes. The information about the White Fang attacking Haven was false information to lure Blake into a trap set by Adam! She will escape somehow and find out where the real attack is going to happen. She'll rush to her friends to tell them, but it will be too late! Whichever school the real target is will be destroyed by the end of volume 6. By this time Salem will realise that the relic there has been removed beforehand, like at Beacon. We will learn that Ozpin knew all along that something was coming and was always two steps ahead of Salem. Volume 7-9 will then be the remaining school and all the teams we've met preparing for the final battle against Salem. Oscar/Ozpin will join Jaunes team and it will be named team ORNJ(orange) and tell him that he has two of the relics since he embedded Pyrrhas in his shield. With the cane team ORNJ will have 3 of the relics against Salems 1 relic. At the end Lionheart will sacrifice himself to get the one relic back, because he was working for Ozpin all along and only gave her the relic to get her trust and distract her from the fact that the other relics were not at the academies anymore. With the power of all four relics combined they will finally defeat Salem!
Some smaller predictions what could happen between the big plotpoints:
The relics can change their appearance. That makes it harder to find them and is also the reason why Cinder did not take the cane and the headpiece with her, because she didn't know those things were relics. Ozpin could've embedded the one in his cane just so nobody finds it! The sword of the Arc family could have been altered to fit the current owner. It can have a different hilt and parry from the one the king used to make it more balanced for his son, grandson, great grandson you get the idea. The headpiece of the Nicos family could have been a bracelet or any other kind of protective item. Can't say anything about the last one, because I don't know how it looks!
Penny will return. I feel RT is trying to mislead us with telling us she's gone for good!
I will not go into detail, but we've never been told in universe how robot souls work and if the soul leaves an artificial body if it is turned off or only when the brain and memories of that unit are completely destroyed!
The power of the relics combined could be strong enough to bring Pyrrha back, but that's just wishful thinking at this point, because we don't know how powerful they really are! They could turn out to be some kind of Deus Ex Machina like the Dragonballs and have that much power when they come together!
Jaune has seven sisters. I believe the chance that one of them might be a maiden is pretty high! Why would he mention it that much if it wasn't somehow relevant?
The Spring Maiden is part of Ravens clan. For all we know it could be Neo(or Coco but I think that's more unlikely)! They all wear the same necklace, which could be a symbol for her tribe!
If turning into a bird wasn't Qrows semblance then it could be a possibility that he and Raven are Faunus. Or that there is some weird magic out their that can turn people into animals. If they're Faunus Raven could be Adams mother, making him Yangs half brother!(just speculation on this one) I don't really think they will go that route, but if they do, learning that he almost killed his sister will force Adam to reconsider his actions and change.
Cinders weakness against the silver eyes is because that insect Grimm she used to steal the Fall Maidens power fused with her body(the glove disappeared after the transfer) making her part Grimm!
Summer Rose is really dead. I know some believe RT is trying to pull a Vader making Salem go all "No! I AM YOUR MOTHER!" on poor Ruby, but I think that one is BS. It was one of the biggest plot twists in movie history, but that's exactly why I think it wouldn't work a second time. It's too well known and too many people would expect it today! I would be very disappointed if RT couldn't think of something more original. Also, I believe when Hazel said in the beginning of V4 "Yes, we dealt with her kind before!" after Dr. Watts mentioned "The girl with the Silver Eyes" this was clearly a reference to them killing off Rubys mom!
I don't know how many of my predictions hit home but I think I can trust my gut with most of these. These are just my thoughts after Volume 4. Some of those might change after I get more new informations within one of the future chapters. But with the info I have now, I'm like 90% sure that's how it's supposed to continue. After all I can tell you how a book or movie ends by the time I'm halfway through. Bear in mind that I've never read any official statements made by Rooster Teeth, because like I said before they could willfully lead us into the wrong directions!