Oh god, we're talking about overclocking SD cards? I can't wait to see experimental results not only in general, but also in edge case scenarios like when encountering counterfeit hardware.
Of course, the maximum bus speed of SD cards right now (including the UHS-II hardware change to add additional contacts) is only ~300MB/s, with a more practical top speed of ~150MB/s to allow both reading and writing. Maximum power consumption of UHS-II SDXC cards is 2.88W, which is actually fairly significant when you consider the volume of the cards - it's not a lot of power, but it's also not a lot of thermal mass.