Anything up to 32GB should work fine. The SDXC changeover probably wont affect us (which means you can use them without issue, as long as you can work around the exFAT issue), so I'm fairly certain you'll be able to use any Mini/MicroSDXC cards that come out. Linux would actually support 2TB just fine with SDHC (the limit on the spec is basically arbitrary—likely to generate more memory card and device sales), so there shouldn't be any issue.