I've been running with a theory I haven't seen pop up quite yet but here it goes. Team RWBY will become the hosts of the four maidens before the shows end. And we've already possibly seen two of the maidens behind set up to be taken.
Fall- the first fall maiden we meet is Amber who is ambushed by Cinder and friends, after being severely injured she is taken to Beacon where her powers are started to transfer to Pyrrah but is interuppted by Cinder. Battle Insues and Pyrrah, to everyone's extreme sadness, dies. Cinder seems to gain all of the maidens power. At one point we see that Ruby is hearing Pyrrahs voice in her head. Leading us to believe that maybe whatever maiden ability Pyrrah had may have been transferred to Ruby instead of Cinder. But fast forward to the last couple episodes of season 5 and we get a fight between Raven and Cinder and seemingly see Cinder fall to her death while being frozen solid. Let's say she did die there, the Maiden power would try to seek out it's other half being transferred to Ruby. What is no power was given to Ruby after Pyrrahs death though? The power is transferred to the last female in the mind of the Maiden before death. Who else would Cinder be thinking of except the woman she most despised, the woman she vowed to kill no matter what, Cinders last thought, would have been of Ruby meaning the power would transfer to her.
Spring- this one is pretty simple connection, the current maiden is Raven who is Yangs mom, Raven is on a very fast death track and could be dying here pretty soon. When she dies the only girl that could come into her mind would be her daughter, Yang. So when Raven dies all her maiden power gets transferred to Yang.
The next two I don't have any knowledge of we haven't seen or heard from them.
Winter- if you want to speculate I would say that the Winter Maiden is actually Winter Schnee. I have no proof or even facts to even start to back that up I just think it all fits snugly. Winter Schnee the Winter Maiden to pass the Maiden ability to her sister Wiess after her untimely death.
Summer- by process of elimination that would leave Summer to go to Blake, but that's all I can say, i don't even have speculation on who the summer maiden might be.
It's not a strong theory but I think they set up Ruby and Yang quite nicely and it could make sense that this is the route they are going.
I'm sorry for anything that may be incorrect in this theory I tried to do research but I'm bound to miss something or mess something up.
But there it is! What do you think?