Peridot, while in full-on Saturday morning cartoon villain mode at the beginning of Friend Ship, said that the Earth had an expiration date and she didn’t want to be around to find out when. Think for yourself what the odds of that being an innocuous reference to the Sun’s destiny to turn into a red giant and engulf the Earth.
Yeah, not too likely, eh? Well, then what could she be talking about?
What can we gather?
It was just a quick reference to Earth’s fate that Peridot made, and the Crystal Gems were too busy trying to apprehend her to notice it and question her. We can only gather precious little information from the remark.
First of all, the obvious ones that she outright stated: she doesn’t know when this “expiration” will occur, and it isn’t something that would be pleasant for a Gem to experience. While it’s certainly possible that she merely meant she didn’t want to spend any more time on Earth, anything able to cause that much damage to a planet must be quite strong and that phrase is usually used to mean that sticking around would be bad for the speaker (and, therefore, will be bad for the people she’s speaking to, hence its utility as a taunt).
As for what is implied, the expiration date is clearly related to the homeworld. There is little reason why Peridot, who has been on the planet for months at most, would know about something that the Crystal Gems, residents of the planet for thousands of years, didn’t know about unless it was a homeworld secret.
I already got what I needed!
The first thing to come to mind is the gem shard fusion experiment the homeworld had been running. The impending maturity of the samples is apparently what caused the Red Eye to be sent on a scouting mission, and why Peridot was sent to Earth to check on the Kindergarten, first alone then escorted by Jasper.
All of the forced fusions in Keeping it Together that had been kept at the Kindergarten were made from the shards of Crystal Gem rebels, but we know that many gems were shattered at the strawberry battlefield. The monster that confronted Garnet may have been content to merely hold her, a former ally, but what if it had been made of former enemies instead? A fusion of homeworld gem shards could be very dangerous.
So that’s one possibility: Peridot was sent to Earth to check on the maturing fusion samples at the Kindergarten. Made up of former enemies, the experiments were small and weak, probably just to test the concept. But what if, somewhere, there is a massive cluster of homeworld gem shards fused together? Once Peridot saw that the experiment was a success, she could have initiated some final stage of preparation. All there might be left for her to do is wait for the homeworld’s newest soldier to emerge, and perhaps get a bit of exercise playing with the Crystal Gems while waiting for the homeworld to take it off-world.
Of everything we know about, this is the most likely cause for concern. The only other thing we know about that could be dangerous enough would be the breaking of the geode, either from general wear or because Peridot sabotaged it. Beyond that, there are all sorts of terrible fates that could befall the Earth. It will be up to everyone to keep watch for clues in later episodes.