Well, the most relevant to come to mind is who is Sardonyx? This gem is upcoming in the next Stevenbomb, a bunch of episode coming at one, so who do you think she is? Do you think she's a fusion, a home world gem, a crystal gem? On the teaser is says, "Sardonyx is coming!" That may mean she is evil. A Sardonyx mineral is brownish white so she may look like that. What do you think?
Well I'm always hoping to see Garnet and Pearl fused but based on the color scheme it definitely looks like she has something to do with Jasper. Although with SU you never know.
I have two main theories: One, she's a Crystal Gem from the war that they now have all of the gem shard pieces to and Steven heals her. Two, we get a taste of Homeworld and she's trying to conceal that she was a CG in the war.
"Sardonyx is coming!" does sound evil though, doesn't it?
I hope she isn't a fusion honestly, we just saw Rainbow Quartz. I'm a little disappointed we have a whole week dedicated to one Gem. That's pretty unlike what the show's been like so far, I've gotten used to just getting little glimpses of new things.