So Flamekin are just Fire Genasi and Rimekin are essentially a new Frost Genasi stand in, modeled after the same layout of the other Genasi. Makes me hope we get the other paraelemental Genasi.
Also between this and the Forgotten Realms books both referencing back to Mordenkainen’s often, seems pretty clear that those species aren’t getting updated in a book anytime soon 
not that they needed it.
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