Sprint has released an official Android 4.0 update for the Evo 3D, almost all users must be curious and want to just try to install it on their device, even though they are still in the unlocked bootloader and has installed a custom ROM and custom recovery (TWRP/4ext). You might not get the OTA update notification from HTC, even when you check it manually, the reason is that you aren’t on the stock ROM and stock recovery. If you have an unlocked android phone via HTCDev and S-ON Hboot 1.5 We recommend relocking your Evo 3D and updating it with stock 2.17.651.5 RUU first before doing the update via OTA ICS.
For those of you who in S-OFF state, you’re not recommended to perform an OTA or flash PG86IMG.zip (which contain hboot.img) as it will automatically upgrade your Hboot to 1.58. In case you keep doing an update, your device will remain in S-OFF state, but with Hboot 1.58. I personally prefer to wait and download a flashable ICS stock ROM (that already rooted, and debloated deodexed) via TWRP or 4ext recovery, there are developers who already worked on this.