Nikon(like Canon) is relying on the bored nature of digital practitioners from their tools. Soon they need(or want) to change for better look and to avoid being lagging from the herd, it's the same trend since started 15 or so years. They already have the latest Nikon AFS Nikkors and every thing made easy to them to decide for getting the newer mirrorless body.
Plus, potential emigrant customers to Sony.
Sony, and much earlier, provided the best designs/sizes digital camera bodies for its customers, while at the same time Canon/Nikon continued re-building Film Style Tank size digital cameras.
Photographer who own old Nikon SLR lenses, will not be attracted by the 24MP Z6, I think.
But, Nikon Z7, is too much pricey to be justified for old Nikon SLR lenses, alone.
Nikon expectations is not stupid, just simple studying the herd buying behaviorism since 15 years, I think most owners of Nikon DSLRs will also buy Nikon Z bodies.
Based on what's already provided/expected by Canon/Nikon, I do not think Sony customers and also immigrants to Sony customers, will think to comeback to Canon/Nikon.