HTC will be selling an unlocked version of the One A9 which will work on GSM networks like T-mobile and AT&T. One of the most exciting parts about this variant is that it will be bootloader unlockable via the HTC dev website, but wait it gets even better! Unlocking your bootloader will not void your warranty!
In the past making software modifications would automatically void your warranty. This has always seemed very unfair. It meant that if you installed a custom rom and your charge port stopped working you were out of luck even though the software had nothing at all to do with the hardware defect. HTC has decided they will make good on their hardware no matter what you do to your software. I wish other OEMs would take this stand. It would be nice to have all radios in this device. My carrier is Verizon, and I am sure the Verizon variant will be tightly locked down.