The HTC One (M8) for Windows launched as a Verizon-exclusive but AT&T was quick to announce that this is a temporary exclusivity and put up a signup page. There's going to be an international version, which was certified with Euro LTE bands.
The international version has passed through the Wi-Fi certification body. The certification document doesn't reveal much just the Wi-Fi spec, which is dual-band 802.11/a/b/g/n.
There's no word on how long Verizon's exclusivity will last but it's collecting all the necessary certifications. The Verizon version already got a price cut so we can expect the GSM model to launch straight at that price.
You can read our preview of the HTC One (M8) for Windows (the Verizon version) for more info on the device.