Yes, though that would mean they need to stack three drops for red, green and blue, rather than two as in CMYK. Which might create some quality issues. At least CMYK printers avoid the triple stacking for black which CMY printers would have to do. With CMYRGBKW there would be no dot stacking (subtractive color mixing) required at all, resulting in less required ink. Though needing eight base inks rather than the five in CMYKW might be a larger disadvantage.