I fully expect Nikon and Canon to release cameras that will better the a7rIII on most fronts, including battery life.
They fully understand that Sony is the leader with a huge lense line-up and that they must do better to attract customers. At least Nikon with their choice of a new mount can only rely on superior performance. If Canon goes the route of a mirrorless 5DIV then they may be hoping that existing lenses may keep their existing customers on board even if performance is somewhat inferior on some fronts. The usual marketing and sales tactics will probably compensate.
Cheers,
Bernard
Looking at my magic ball here... that it is usually more wrong than right... I don’t really expect that Canon or Nikon to be better in most fronts... what they really need it is to demonstrate that they are really investing into pushing those cameras... like showing a good lens roadmap... like Fuji is doing...
Although they have an advantage in native lenses... designs for Sony FE from voigtlander, Laowa, tokina manual lenses, Samyang manual lenses and Zeiss Loxia line...
When third party manufacturers reverse engineer the electrical part of the mount, probably you will see Tokina, Tamron, Samyang and Sigma lenses (highly doubt Batis line of Zeiss is adapted... Zeiss never released AF lenses for mounts they could not get the specs from the manufacturer... although rumors say the AF lenses are a Tamron design, so maybe Tamron release them under their brand without Zeiss coatings).
Also, the perspective has changed... it is not that Canon and Nikon need to demonstrate that mirrorless are an interesting option for the future like 5 years ago... Canon and Nikon users will invest in the system if it is good... it does not need to be the best... that can come latter...
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