GUYS I HAVE A THEORY! they aren't going to kill shadow milk, and I think I'm pretty certain this time. so, as much as I hate the idea of the whole souljams are holding up the universe/timeline thing, it is part of the lore now. the only reason we have and need the light of solidarity/"radiant cookie" is because without her, the souljam presence or something would be thrown off. this means devsis has two options, or they contradict themselves:
1. kill pure vanilla AND shadow milk and merge their souljams to create another thing like light of solidarity cookie, as to not throw off the souljam thing, because I believe if just one goes than it is thrown off, but both is okay because it worked for white lily and silent salts.
2. keep them both alive and reuse or redeem shadow milk.
I don't think devsis wants to kill pure vanilla (dear god, I hope not..), so to not contradict their own, already contradictory, lore, while also not killing pyuba, they just need to keep them both alive. same goes for hollyberry and sugar, cacao and flour, and cheese and spice.
or I'm crazy and none of this is right. I don't even know anymore 😭