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Go ahead and stick with your 500mm. This zoom lens is lighter and less expensive, and is not being marketed to replace Canon 500mm lenses.
I don't think anybody said that is was going to replace a Canon 500mm, but if IQ is important, what I am seeing so far is softer images in which case there is a decision to make between weight/convenience and IQ. That of course is a personal decision.
There are cases where I have rented a 400mm DO because weight was specifically a concern and obviously this new lens would be a consideration for those instances as well .
It's obvious there is a lot of excitement over this new lens (similar to the A7/r release?) and I also hope it is a good performer - who wouldn't. But, it looks like the excitement has gone to the point where someone will post a link and claim sharp images and then when I followed the link the images (at least to my eye) look rather soft.
As we get more info about this lens, I certainly hope that things look better.