According to Nikon’s website and based on the translation, it reads, “Regarding the following models that were scheduled to be released on July 28, we will postpone the release in early August, as it takes time to final adjust the product. We sincerely apologize for the inconvenience incurring a great deal to customers waiting for product launch.”
As for Canon, note that the delay only seems to apply to the EOS 6D MK II with the kit lens bundle. Canon’s website reads, “Digital SLR camera that we are planning to release on August 4 EOS 6D Mark II · EF 24-70 F4L IS USM Lens Kit We are currently receiving very many orders that exceed the plan and deliver goods It is expected that you will receive your time.”
Based on the wording it seems that this only applies to those who want to purchase the camera with the kit lens, which means that if you don’t mind body-only then you might be able to get your hands on it earlier.