So, firstly, i apologise as i didn't know that there was the Volume by IR option in the ATV. So Kring is asking that question as an extension of that.
I've just got home and set my ATV4 up (which i finally have after putting in an order on the first day), and well low and behold i have done precisely nothing and enabling that option is controlling my samsung TV by IR. Well there you go hey, there is more to this new ATV that meets the eye! That will teach me for replying before I have the product in hand won't it!
Changing to the Receiver via IR option is controlling the Denon receiver volume by IR perfectly as well!
Honestly i thought all the control was being done by HDMI-CEC, id be very interested to know more of the back end of the way they have this working. CEC was enabled on both products when i plugged in the ATV, given there is no other set up involved to get that IR working, it would seem they are picking up the control info through that protocol. Very interesting.
TrueBlou, yes they could do of course, though my guess is that problem might snowball for them though. EG how do they deal with TVs that have discrete IR codes and a factory remote only has the discrete on and off buttons. Then you have a issue of buttons and button labelling to try and make work.
Edit, the point I am trying to make there is there a mountain of combinations that exist that may be hard to cover in an auto programming scenario .