The updates to the Z6 and Z7 have a lot of folk wondering whether or not the older versions are still viable. Short answer: they've been viable for two years, what makes them unviable now? Nothing, really.
As I've noted several times, Nikon walked a narrow path with the Z6 II and Z7 II. Yes, they corrected the most commonly heard complaints about the original models (single card slot, no vertical grip), but really only added one other new significant thing: a second EXPEED6 that allows for some additional autofocus modes and performance. Nikon didn't out-and-out invalidate the Z6 and Z7 with these updates; there's no reason for most Z6 or Z7 owners to update, really. The originals are still perfectly fine cameras for most people.
So the only real question in my mind is whether or not Nikon's pricing is correct. As I write this, it goes like this:
- US$3000 — Z7 II
- US$2600 — Z7
- US$2000 — Z6 II
- US$1800 — Z6
- US$1300 — Z5
Nikon seems to think there's US$200 differential between the Z6 and Z6 II, and US$400 differential between the Z7 and Z7 II. They want you to think this: "if I don't need the 3 big new things in the II models I can save some money." Some folk will (and should). The only question is whether this is the right price differential. I'd say no. The Z6, for sure, needs to come down some more in price. It can lure Z5 tire-kickers up, and Z6 II tire-kickers down if priced right, and I'd say that's probably more like US$1700, possibly US$1600. Or perhaps a better choice for Nikon would be to bundle an XQD/CFe card with the Z6/Z7 at the current prices.
I do think that the Z5, Z6, and Z6 II is stuffing just a bit too much that's similar into a small space, which can make sales volume actually smaller rather than bigger if not matched with really good marketing. But any dealer worth staying in business would know how to steer a customer between these three competing models.