I honestly didn't expect it as just a secret rare, to be honest. Don't remember any card not being released as a SM-era print, but getting a SM-era secret rare.
There's still the hope of it being part of the Rayquaza set (we originally got it on Roaring Skies after all). Besides, at least up to Forbidden Light we've gotten at least one secret rare energy in each main set. Since all that'd be left is rainbow, it'd have to be either that or a new one released in said expansion (which could be DDE, or some new energy concept also thought for dragons exclusively! ...or just some other, unrelated new type of special energy).