Full disclosure: I'm still implementing MLC shrinking between doing other things, so at this exact moment it's 16GB for 8GB, and 64GB for 32GB. Those numbers will stay the same for users who don't wish to shrink their MLCs. After MLC shrinking is fully implemented (and it's getting there, debugging it is just really exhausting), all systems will be able to run off of just a 16GB card. MLC sizes smaller than 8GB actually seem possible, but I'm not sure yet if I want to support them since Nintendo themselves have likely never tested sizes that small.