I’ll give a rather different take on this - and why it isn’t a marketing gimmick.
As has been noted - the receptors in the eye are not a simple set of red green blue - they have astounding amounts of overlap - so much so that the actual colour, at any wavelength, is determined by a balance of all three. You can think of it like this - for any wavelength the three receptors have different responses - so for any wavelength we can calculate what that wavelength is by looking at the three levels. Also, the eye creates representations for colours that are not spectrally pure, with representations for washes of colour across a range of wavelengths and light made from discontinuous sets wavelengths - i.e. colours that don’t exist in the classic spectrum of white light.
But, because of the overlap in the receptors, you can’t cause they eye to detect all of the possible combinations of levels by shining a combination of three wideband colours into the eye. You can only do it with light of exactly the right wavelength.
The problem is to convince the eye to create some approximation in its receptors to the levels your camera obtained. Because you only have a wide slab of spectrum for each of red green and blue, you are very limited in your ability to stimulate the eye’s sensors in a controllable manner. If you turn up the green levels the blue and red levels in the eye also go up. In the end there are simply a large number of colours that you can represent in your colour space that you can’t actually get the eye to generate for your brain from simple RGB light combinations. In the extreme, what you want is a display that allows you to select the exact spectrum of light that each pixel generates. Which we don’t know how to do. But a simple start is to start to split the spectrum up into smaller segments - and splitting green into a deeper green and a yellower green is probably not a bad start. It will expand the range of colours by decoupling the response of the different sensors a bit further.
There is another technology. If we are able to generate a lot of light at very deep blue - say 400nm, and very deep red, say 700nm, and green at exactly the point where the green and red receptors start to diverge in sensitivity - about 550nm - we can stimulate the eye to generate signals that cover close to the full gamut. The only way at the moment is with DLP projection and laser light sources.
A related point about any form of colour reproduction is that you can’t create a colour that isn’t in the base illumination light. Since plasma, crt, and until the advent of LED backlight, all LCD panels were based upon phosphors, the gamut was limited by the wavelengths present in those phosphors. The DVD and BlueRay colour gamuts are based upon these phosphors. This standard places some intrinsic limits on what you can usefully do, since the conversion from film will be limited to colours inside this gamut, and even if your display can create colours outside that gamut - they won’t be in the encoded source. There is a suggestion for a new wide gamut standard, but I wouldn’t be in a hurry to hear much about it.