Currently ALL flashcarts so far still use the microSDHC standard. We would have to see a microSDXC supported flashcart. Otherwise the file size limit of FAT32 becomes more noticeable.
(sorry if I still don't get it) are you telling me that there's no way that we will be able to use multi-rom on mt-card/gateway with games >= 4GB?
edit: thanks, kyogre! PHEEEW....