It says it supports up to 16GB ones because 32GB weren't out at the time when the N900 was released, so saying you support a future device is always a crapshoot for companies, so they don't bother. However, the N900 can pretty much take SDHC cards. It shouldn't be able to take SDXC cards, because it doesn't support the format, but AFAIK, it'll be just as capable of taking other higher capacity SDHC cards when those come out too.