Now that Edison is ruled out, it looks like there is only three choices now.
Also Lilith being turned into stone, 100% rules out a fake out with York being a traitor. I know some thought that York being turned into stone could have been a fake out, but the fact that Lilith got turned into stone as well pretty much rules out York now.
The mysterious culprit is either Atlas, a 7th satellite, or another 3rd party.
Whoever it is can order the Seraphims, and the only ones that can do that are The Five Elders, The Vegapunks, or someone with a authority chip.
The fact that none of the Vegapunks could order the Seraphims, at least rules out someone with a authority chip.
So I guess it's either Atlas or a 7th satellite unless for some reason it really ends up being Devon or Laffitte.