Yup. The HTC One HAS a microSD card slot, but only for the Chinese and Japanese markets.
Can't stop me from trying to import them. xD
Be careful when importing one. ie the Japanese version is a CDMA device, sure it has roaming capability on GSM/HSPA, but as usual CDMA operators (AU by KDDI in this case) are notorious for refusing to unlock phones.. Actually only one operator in Japan unlocks phones (NTT DoCoMo), and it's a concept they championed not for the good of users but because they wanted iPhone users to use their services instead of their competitors'.
On previous HTC J phones sold on AU, there were talks that if you flashed some international ROM and radio image on it (The HTC J Butterfly, to be precise) it would effectively turn into an unlocked, international, GSM/HSPA variant HTC Butterfly. While it may or may not be possible with the HTC J One, I'd wonder if flashing an international ROM would at the same time completely remove access to the sdcard, since international models don't have it.
THAT being said, there's quite a long thread on XDA's HTC One forum about the Chinese variant and the troubles and joys they go through to make it work in their country of choice, rooting it, etc. IIRC, the Chinese variant doesn't come with Google's apps, so that's already a big minus except for the most paranoid of us who want to avoid Google's services...