The article brings up some good points regarding using EF lenses on mirrorless. It also may explain why Canon (and Nikon) have not jumped into the FF mirrorless arena yet. Rather than being too conservative, or too slow, or whatever term the usual critics like to use, Canon has a problem that Sony did not have; how to create a FF mirrorless camera that maintains a high level of AF for its existing EF lenses. Sony did not have an existing lens lineup anything like Canon does nor as many users that would be upset at the slower AF speeds when using legacy glass on their new mirrorless offerings. Olympus, while not FF, had many upset users who couldn't use their 4/3rds glass on their new Micro 4/3rds due to slow AF. They tried - somewhat successfully - to allow users to still use their 4/3rds glass on the new E-M1, but it was still slower in the AF department than native lenses. Canon, I would think, wants a seamless transition to mirrorless for those using EF lenses (whether they keep the existing mount or will supply an adapter), so they wait until they can get it right without losing AF speed.
