I'm sure they will. I guess because has yet to display any real concern for any human other than Steven is why they didn't take her with them. Plus, the smaller the group, the better.
Well Peridot did say to Jasper that Earth is full of life so she does show concerns. She and Lapis have an opportunity that the Crystal Gems never took advantage of - Peridot and Lapis don't have to wait a few thousand years to truly interact with humans.
Yes, but remember how she acted towards Greg. And like I said; for an infiltration mission, a smaller team is better. And the Crystal Gems have much more experience as a team without Peridot.