HTC adds Verizon and AT&T devices to bootloader unlock tool
The reports had started because an xda member named nightwings had found that the unlocking tool successfully unlocked his HTC Rezound, and users in the HTC Vivid forum were also reporting success in unlocking their devices. More tests found that the HTC Thunderbolt and HTC Rhyme could be unlocked even though the HTCDev tool didn't officially list them.
The list should be updated soon, but if you're looking to unlock the bootloader on a newer HTC device, it is looking like it's possible. HTCDev said the team is still working on adding compatibility for older phones.