"I don't know if any other manufacturer has a faster lens with IS, but I suspect not."
Firstly, 50s are the easiest to make fast. Secondly, this is Canon, is it shocking that they are ahead with lens technology? No. Thirdly, this is 2012, technology is improving fast. Of course this is possible.
Then again, where's my 24-70 IS?
5Ds, 5D3, 8-15 f/4 L, 24L II, 35 f/2 IS, 24-70 f/2.8 II L, Sigma 50 f/1.4 Art, 70-200 f/4 IS L, 85L, 90 TS-E, 100 f/2.8 L, 135 f/2 L, 600EX-RT x2, CS6, LR5