Oh, how we loathe the word "exclusive." For those of us on the editorial side, it's become a bit of a joke. But when a U.S. carrier uses it, it means someone else is probably getting the short end of the stick. In this case, it's anyone not AT&T, which is boasting in a promo video that it's got the "exclusive" on a 64-gigabyte version of the HTC One. AT&T announced all that back in February.
That means if you were hoping for the larger storage options on T-Mobile or Sprint, you might not get it, at least not at first. That said, the vast majority of "normal users" will never come close to hitting that 32GB limit. If you're holding out for a Verizon variant of the HTC One, we'd be willing to bet that 64GB might still be on the table.