Refreshing to note that we have practical minded people here who understand a huge chunk of our hobby is simply driven by the display / television market, and it is what it is.
RGBY for display offers significant gamut improvements over RGB. The problem is that LED or regular solid state light sources that generate yellow are far more common and economical than yellow emitting laser sources. The key driver with display technology though has been RGB...for now. If yellow based diodes were available for the same price as blues and reds I can guarantee you we'd be seeing them in higher end sets. I spent 3 hours eyeball calibrating my old man's Mitsi laser TV, and while it was excellent in the end the additional yellow channel would have helped - a lot.
On the other end I've been arguing for about a decade that RGB is more of a problem for digital capture. We need a minimum of an additional color filter like yellow, and a mid blue would help as well. RBG is fine for DJ lights, but it's highly limiting for display or aquisition.
That, and a 2watt yellow would look utterly bad-ass in my projectors. :evil: