Doesn't really do S5 owners any good if the phone doesn't recognize anything larger than 64GB.
Not out at the time of the press release, most likely. I'd suspect a 128gig SD will work as I don't believe it's anything like the issue with 4gigs of ram and 64bit.
For example, many phones claimed "32gig" cards as compatible but had no issue with the 64gig card.