The reason for the question is that a 300 f2.8 is a little too long for ice hockey shots, at least some of them, and the 70-200 2.8, my main lens, is a little too short for some shots. I figure a lens like Sigma's would be just about right. And I agree, if Canon ever comes out with one, it would be ridiculously expensive but I'd bet it would be a popular lens if the IQ is on a par with the 70-200 2.8. I understand that Sigma is releasing or has just released a second gen of the lens but if it is out it's too soon to tell whether it's really an improvement.
That's for the replies.