Remember this?
That event happened as planned and they now released an article and pictures of it.
It certainly looks pretty cool, although I think the effect would be lost in a venue beyond a certain size. I think this kind of thing would be best for exclusive events with a small audience with max. 100-200 people so they can all be close enough to the stage to get the most out of the 3D effect.
I don't know about the viability tech and budget wise. They used the Quest 3, which as far as mixed reality headsets go is cheap, but it's still a $300 piece of equipment you have to lend to every person in attendance. They mention using phones instead, but I think that would be a lot more boring than actual MR glasses.
We'll see. It should be relatively cheap to produce special headsets. Quest is definitely overkill and kinda unsuitable for the application (i don't think any existing VR headset position tracking gonna be reliable with that density, they need to have more sensors on the top and none on the bottom). Basically it only need to play video overlay over camera pasthrough, all rendering can be done much easier and better server-side. With WiFi7 it's easy to do personalized video feed to each viewer in small venues, and for bigger ones this format is obviously non-starter.