It's very possible but unlikely until the next version of the device. Basically you would need an IR transmitter that had a web endpoint and could control your TV/set top box. I have ridiculous hacks where I set an alarm/reminder to say "Xbox turn off" around bed time.
Since you might be more up to date with what echo can do.. could it work as an ad-block for TV (mute, switch channel)? Perhaps using 3rd party API for tagging ads.