We had G.722 support for a long time. My estimation is that less than 0.01 percent of the calls were using it, even though most phones support it. There are a few things to keep in mind here.
First of all, we have to keep in mind that every kind of transcoding reduces quality. Audio quality never goes up, even when using a great codec. If you are on Opus and then the call gets transcoded to G711, it sounds not as good as everybody using G711. That being said, there are very few (no?) SIP trunk providers that offer anything better than G.711.
Internal calls may have great quality. The problem is that they are usually not the call generating revenue in businesses.
Most modern HD codecs were written for client devices, meaning that CPU usage is not a big deal. However when you want to have 500 calls going on in the PBX, it is a big deal.
It is debatable, but IMHO there is a certain user expectation about how a office phone system should sound like. When IVR sounds narrow band, callers have that warm fuzzy feeling they are talking to their good old (and reliable) phone system.
From a sales point of view, Opus and HD are indeed a great way to wow new customers. That is currently probably the most important point.
We have added Opus to the development branch, however this needs to be tested first and made sure that it does not cause any harm. We need to change the default priority of the codecs and put HD first. Otherwise nobody will ever experience HD audio on the Vodia PBX. We found only a few Cisco and Polycom models support it today. Its a chicken egg problem obviously, and the PBX should take the first step.