JCase and TheRoot.Ninja team have released S-Off for the HTC 10 prior to the phone's release! For now the app will only S-Off your HTC 10. You will still need to unlock the bootloader using the HTCdev website. This is still big news as S-Off allows you to flash whatever you like to the phone. This means you will be able to run any Rom you choose.
Unlocked HTC 10 units should be shipping this week. If you decide to go ahead and S-Off your device you should know that once you are S-Offed if you change the lock status or the s-on/s-off status the phone won't be able to decrypt data until you wipe your data.
The full S-OFF sunshine app PSA can be found here.