If I"m not mistaken, the current SDXC Cards (or at least some of them) are just "SDXC in name only", and actually comply with Version 3.0 of the SD standard – the same as SDHC. The only caveat is that they come formatted as exFAT, which can only be used on Microsoft Windows. You should be able to format them to something usable with Linux, though. There"s a bit more about this here (my apologies for it being a Wikipedia link – it is a decent enough quick overview, though).
Obviously, this won"t apply to Version 4.0 SDXC Cards, which I gather are physically and electrically different.