Will Roku ever be offering an update or an app that allows the Roku stick to support antenna TV in the user interface?
If by Antenna TV you mean watching local over the air broadcasts, the answer is no. That requires hardware, an ATSC 1.0 tuner, that no Roku player has. Only Roku TVs have an ATSC tuner.
If you mean to access the TV tuner that is contained in the TV the Stick is connected to, the answer is still no. That requires the TV to have an interface that permits something connected to the HDMI port to access the ATSC tuner. No TV has such an interface, and unlikely they ever will.
There was an earlier version of the Roku Stick that supported the MHL standard, which did allow the Roku to control the TV itself. Those are no longer available and unsupported by Roku, and TVs with MHL ports are few and far between.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution." If you appreciate my answer, maybe give me a Kudo.