This is my prediction and if it comes true my mind will explode.

We already know that there is a major theme of destiny vs choice. Even the rebellion leader, Rose Quartz, who EVERYBODY claims taught them to make their own choices, believed that gems are manufactured to think a certain way when they come out of the ground. This seems to be the case for ALL the gems except for the Diamonds who seem to have their own personalities.

My prediction is that, as seen from the lack of pink diamond in command in Monster Reunion, is that Pink Diamond is dead. But before she died, she thought differently than the other imperialistic diamonds and acted on those feelings.

Long story short, she made Rose Quartz be the perfect rebel against Homeworld. She programmed Rose Quartz to have the ideology that gems can think and act on their own desires so she could teach others and start a movement. And, much like I, Robot, she had Rose Quartz kick off the revolution by killing her, giving other gems the thought that the Diamonds are defeatable.

I always suspected that Rose Quartz killed (or did "something" to) Pink Diamond, but Jasper being a loyal soldier of PD? Quite the twist.