I'm sure that I speak for a great deal of RWBY fans when I say it would be incredible to see Team RWBY get back together again, and while I realize that such an event is more than likely (given the final scene featured in the new intro "The Triumph"), I don't want to set myself up for dissapointment, so I'll just keep an open mind. That said though, I have a theory I'd like to propose to anyone interested...
Let's make the assumption that Team RWBY will eventually reunite in Volume 5. My prediction is that Team RWBY will reunite in two parts: first, in seperate events, Ruby and Blake will encounter each other while Yang finds Weiss; then, in some sort of scenario, they will all reunite back together (a scenario that likely has a lot more depth than the slipshod, simplistic sentence I just typed '-_- ). Obviously, the last scene in "Dread in the Air" will indicate why I paired Weiss with Yang. As for pairing Ruby and Blake, this was a bit more complex, and, honestly, I really don't know if it's gonna happen, but wanted to see what others thought anyway.
There are two core reasons why I think Ruby and Blake will meet up. The first involves problems with group chemistry between Blake and Yang, and the second relates to where both characters are positioned in volume 5, both in context of location, and to the plot.
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Towards the end of the finale for volume 3, when Ruby asked about what happened to Blake, Yang angrily responded, that Blake ran. She didn't know why, and added bitterly that she didn't care. Did Yang really mean this? I'd like to think not. Granted, I'm not necessarily saying she is concerned about Blake's status, but rather, what happened to Yang's perception of their bond when Blake left her.
Let's rewind a bit to beginning of the RWBY saga. Even before he assigned everyone to the four-person teams, Ozpin said that, after landing in the Emerald Forest, the students would become partners with the first person they made eye contact with; Ruby saw Weiss, and Yang saw Blake. Now, unlike the former pair, it didn't feel like the latter's relationship received much development or even attention until the middle of Volume 2, but when it did, it was very heartfelt. In "Burning the Candle," Yang told Blake about how she put herself and Ruby in danger during her search for her mother, and that she didn't want the obsession to control her, in order to convince Blake to take a rest obsesssing about the White Fang to the point of exhaustion (ironically, during volume 4, Blake initially wanted to forget about the White Fang, and currently, Raven is the only person Yang is looking for).
I also think another moment showcasing their bond happened in "Destiny," when Yang asks Blake if she believes her claim about Mercury attacking her. The moment Blake says "I want to believe you," we immediately see tears in Yang's eyes (I think it was the first time we ever saw her cry). After making Yang earnestly swear she saw Mercury attack her, Blake smiles and thanks her (... so she believes her.... I think...). However, it felt to me that when Blake doubted her, she looked far more upset than when Ironwood had told her she'd been disqualified.
Other than a brief call via scroll at the start of "Battle of Beacon", that was the last time (last meaning most recent, and definitely NOT final) we see the two of them speak to each other; the last time they SEE each other was when Yang selflessly rushed to Blake's aid against Adam Taurus, only to lose her right arm.
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I think it's fair to say the anger and bitterness Yang expressed regarding was created due to not knowing what had happened to her as well as remembering how Blake doubted her about Mercury (speaking of which, I'm betting since "Cinder's Team" is going to find Raven, it's likely will see a certain rematch very soon), compounded with the fact that Blake left her so abruptly; no "I'm sorry, but because I fear for your safety, I think you'd be safer if I left" or even a simple "good-bye."
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Soooo... with all of that reviewed, my first point, is that if Yang and Blake were to meet up with each other, I'm not sure it would work out. Sure, Sun had that talk with Blake about how her friends have the choice to defend Blake or not, but how the hell would he know if Yang really would live through getting her other arm cut off? If anything seeing Blake will bring back this bitterness. As for Ruby meeting Blake, my theory stems from Adam's recent coup for high-leader, and because Sun and the Belladonnas' are aware of Adam's plan to attack Haven, compliments of Ilia's scroll. Also, now that the Branwen Bandits have Weiss (I'm willing to bet that regardless of whether Jaques actually still cares about her or not, Raven and the tribe still think she's worth something), Yang is more likely to encounter her, instead of Blake.
Obviously, I could be wrong, and, because Qrow has emphasized the importance of finding Raven to get the spring maiden, RNJR, Qrow and Oscar may end up meeting Weiss, and/or Yang instead, but, only time will tell... So, what do YOU think?