Yes..... CR discussions never go off topic
...All these lenses seem to be selling well, to my mind it makes sense for Canon to jump into the fray. I can see either a 500F5.6, or a 600F6.3, but I think a 600F5.6 on the long end is extremely unlikely. They may not necessarily be L lenses if Canon decides to compete on price.
I think it does make sense to offer an alternative, but I'm not sure they should attempt to compete on price. With the 100-400 selling for $1,800, I'd like to see what Canon could do in the 150-500 range for an additional $1,000. Sony and Nikon both seem to simply be offering their own branded versions of Tamron and Sigma in terms of quality. Other than brand loyalty, I'm not sure what the point is. I'd like to see Canon stick to the high road and fill out their 70-300 "L" and 100-400 "L" with a 150-500 "L." Preference would be a f5.6 EF lens, but if they were to produce a 7D quality APS-C body in the R mount, then an f6.3 would be fine.