Nikon introduced their first full-frame mirrorless in 2018 with mixed reviews. Some loved it others hated it, but I look at it from this standpoint way back in 1959 Nikon introduced the F mount camera and lens system then followed to build a legendary arsenal of the highest quality lenses to supplement their camera bodies and for nearly 60 years Nikon has satisfied customers from beginner to professional. Do you think that will change with the Z Mirrorless System? I think not.
Although the first Nikon Z7/Z6 full-frame mirrorless introduction is not considered a pro-level camera, like 60 years before when the F mount was first introduced it too was not a pro camera system - it evolved over time, the Z mount has laid the framework for a future to evolve into the highest quality and optical superior cameras and Z lenses that support resolutions sensors of 100mp with apertures as fast as f/.65 - no other camera system will be able to achieve this feat. Imagine a 4 pound 600mm f/ 2.8 - that is the possibility of this Z mount system.
I am standing with Nikon regardless of what other camera companies are offering because I know and trust Nikon's vision for mirrorless.