I agree with Neuro. The only non-Canon L-series lens I own is the Sigma 35/1.4 (I have 9 L-series, from 14mm - 600mm). I have not tested them all, but I have read enough tests to be fairly persistent. But the Sigma 33/1.4 can stand up to any of the competitors, regardless of price. I truly hope they will produce other focal lengths with the same quality. That will put pressure on the likes of Canon, Nikon and Zeiss.
I just saw an add today, where the Sigma sells for just over 1/3 of the price of the current Canon L. So if Canon releases a 35 vII, I think we are in for a treat. Sharpness, vignetting (the only weak point of the Sigma), CA etc. will most likely be stunning. Build quality will be great (but so is the Sigma), whereas IS is not something I will miss, but handy if it is there. f1.2 would be cool tough. But having seen Canon´s price policy over the last years, it is very easy to predict that it will be (very) expensive.