Taping three pins on the Canon 1.4x allows AF to function with an f/5.6 lens...but not well. I suspect that's why Canon locks it out in firmware.
Yup, making more profits by selling faster lenses or the expensive f8 af 5d3 has nothing to do with it :->
So I suppose the rumor of a new 100-400 has died by now ?
Not at all, the *rumor* hasn't died - but the certainty has grown that Canon is currently skimming the top of the market with expensive big whites while retaining good profits with other older designs.
We'll know for sure at the end of the "year of the lens", but if there aren't replacements for 100-400L, 35L and 50/1.4 any further [CR1] rumors can be considered void.