I believe she is going to be the real big bad. But before the gems challenge her there is going to be a lot of townies episode and a couple of episode getting to know better the diamonds as people and not OP space conquerors
Before the series end thou there are certain things that need to be addressed now that they revealed the truth about Pink Diamond, the rebellion and Pearl´s past.
Did Greg knew or at least had some idea of Rose secret?
Is Pearl really a slave or does she has free will?, the way she bypass her conditioning about not telling anybody the truth was pretty clever but I wonder if the other diamonds could in theory order her around like Pink did. I bet there is going to be a moment in the climax where white diamond is going to give her an absolute order and Pearl is going to overcome her metal conditioning to save Steven.
Did Rose seriously condemned all the Rose Quartz in the zoo to an eternity of imprisonment or are they fake like Pink´s shattered remains?
Did Pink seriously played both sides for a good chunk of the rebellion? if that is the case is the Beta kinder garden shit on purpose so the Cristal Gems could have the upper hand?
What was Pink plan with the rebellion before deciding to become Rose forever? The way its framed in the show it seem it was only made as an excuse to justify why the colony wasn´t harvesting earth as the other diamonds intended. If Pink would have managed to convince her sisters/mothers to leave earth alone what would have happened to the rebellion and all the gems that joined to live free?
What is the deal with Rose´s Shield? all gems seem to have a special weapon did the diamond never notice that weirdly charismatic and pink colored rebel leader had the same weapon that their sister?
My money goes that the finale is Steven Blue and Yellow vs White.