The important question is will this be all four "RGBW" in each pixel, will it be RGB/WRG/BWR/GBW, or will it be "RG/BW" (alt. "WR/GB")?
The first would be a questionable decision because it increases brightness of whites but decreases brightness of saturated colors, but wouldn't detract from the integrity of the advertised resolution spec.
"RGB/WRG/BWR/GBW", "RG/BW", and "WR/GB" do that, but also throw out the integrity of the resolution spec, because now not every denoted pixel is capable of being any color it wants. They produce grainy images too.
With this, arguments in favor of it citing power concerns become moot. The actual sharpness is lower, so it isn't fair to compare the power consumption to that of a full RGB matrix display of the same advertised resolution. A better way to save power would be to just use a "lower" resolution, true-RGB-resolution display.