If Xray released a shaft driven car I would sell my Raycer and buy something else, probably an RcLab. Shaft drive is just a fad, exactly the same as the Losi XXX-S' single belt drivetrain. I don't know if anyone remembers this but when that came out everyone was clamouring for a single belt Xray. They obliged, and some pics of development parts broke cover, however, it was never released because it made no difference.
The fact of the matter is that different cars suit different drivers. That has always been the case and always will be. Personally I would far rather have the ideal weight distribution that a belt drive offers than the dubious claim that a shaft is intrinsically faster. My brother has a TC3, and I have raced it on several occasions, and I can tell you that I am much quicker with my Xray. It carries so much more corner speed and is so composed when changing direction where the TC3 tries to break away. I am sure this is down to the weight distribution as every other shaft drive car I have driven doesn't feel the same corner to corner.