TL;DR: Can additive RGB color gamuts produce the perception of light that has a shorter wavelength than the Blue component? If not, does shortening the wavelength of the shortest component of a 3-channel-color system (e.g., "Blue") increase the range of human-perceptible colors producible by the gamut? Is that not done due to technical obstacles?
Digital photography and light projectors typically use an RGB (Red + Green + Blue) color model, which at least superficially makes sense because it approximately corresponds to the peak responses of the three human color receptors:
But humans can perceive light with higher frequency than "blue." Spectrally we refer to that higher-frequency color region as "violet" or purple:
It is not physically possible to produce light with a frequency higher than the Blue component through any combination of RGB color projectors.
We know that a standard RGB color gamut does not cover the range of perceptible frequencies. Here is a standard gamut coverage chart, with the gray area indicating "colors" that cannot be produced by any combination of the RGB source:
Considering the violet region: There is a region in the RGB gamut we refer to as "violet," which is a combination of red and blue. But referring back to the photoreceptor response curves it is distinguishable from true violet because true violet barely stimulates the red photoreceptors.
If we increase the frequency of the highest-frequency component of a 3-color projector – i.e., we increase the frequency of "blue," pushing it towards the "violet" limit of human color perception – do we not increase the coverage of the projector gamut?
I suspect the answer is "Yes. But: the blue photoreceptors are not excited as strongly by the violet frequency. The RGB frequencies were picked to correspond with the peaks response frequency of each photoreceptor. If you shifted the blue frequency towards violet (call this an RGV gamut) then your projector would have to be able to output more violet light than the red or green channels in order to cover the rest of the unshifted gamut." If that's correct then this is a technical issue, and not one that seems particularly challenging. For back-lit projectors, which produce color by filtering a white source, the red and green filters would have to be recalibrated to cut more light than the violet filter.
However the answer might be, "No: See that region between blue and green? No matter how you boost your boosted violet channel it just can't reach into it as far as a centered blue channel." (I think the only way to reach this answer would be to have complete parameters of the photoreceptor response curves to spend some time linear programming.)