I see quite a few people speculating on a ZfII lately. Such a model isn't likely any time soon, so let me explain why.
The Zf is already a Z9-generation camera. That means it has EXPEED7 and all the goodness that comes with that. Indeed, the Zf has some features, such as HEIF and Pixel shift shooting, that haven't even made it into the Z9 yet. It seems unlikely that Nikon would continue to advance EXPEED7 software features in the Zf first. That just puts the Z6III, Z8, and Z9 cameras in jeopardy, and forces updates of firmware upwards rather than in the downward fashion Nikon prefers.
Thus, the only way that makes sense for a ZfII is to change hardware in some fashion. And there we have a couple of issues. First, the image sensor. Yes, you could move the Zf to the Z6III partially-stacked sensor, but then you're undermining the Z6III. Essentially you'd be saying to users "pay US$500 less but you get a retro style body." The whole notion of selling the same basic inside at a lower price doesn't make a lot of sense to me. It's also a marketing nightmare.
Some suggest putting the Z7II image sensor in the camera and calling it a ZfII. Okay, that sort of works, given that you'd charge more for it, but now you have an even further complication for any potential Z7III.
So what other hardware changes could Nikon make? Not many I can imagine. Indeed, the number one hardware change Zf users might want comes in the FTZ adapter, not the camera (e.g. screw-drive and full AI support). Most of the other things I can conjure up are cosmetic.
Let's face it, the Zf sits oddly in the Nikon lineup. Theoretically, the primary lineup fully updated would go Z30II, Z50II, Z5II, Z6III, Z7III, Z8, Z9. The Zf currently sits in the pricing position near where a Z5II would be. The Zf works in the current lineup because of the discounting on the Z5 and the push upwards in price of the Z6III (and the fact that the Zf appeared before the Z6III). If the ZfII has to co-exist with something at the same price point, then it becomes "buy legacy or buy modern," which splits the sales at that price point into two models, which is R&D inefficient.
At the moment, a ZfII isn't anywhere on my future product radar. The current Zf doesn't seem to be under any pressure from other full frame retro cameras at the moment, so I'd bet that Nikon doesn't have a ZfII on their short-term radar, either.
__________________________
Bonus: I keep hearing about a "completely different" design, lower-end model. Call it the Z1. I know this product has been prototyped in some form, but it has not been approved yet by management, to my knowledge. Nikon has a long history of trying to build the infamous "easier to use" high-end camera dating back well into the film era. They even have experience with that in mirrorless (Nikon 1). Nikon also has a long history of failing when they attempt it.
However, one does have to wonder whether the automation we now have coupled with some additional AI might render the controls of an ILC not so necessary (or at least minimized). The problem I see isn't that Nikon wouldn't be able to do the basic engineering of such a camera "right," but that Nikon is not really a consumer-focused company, so I can't fathom them getting the marketing right. For example, I can't see them doing another celebrity promotion as they did with the Nikon 1. I'm not even sure Nikon would know which celebrity that should be (and it would be decidedly different in China, Europe, and the US, complicating the problem). But even at the influencer level, I'm not sure Nikon has the inroads necessary, nor would they be able to react and amplify on that as quickly as Fujifilm did with the X100, for instance.
A Z1 would be at the lower end of Nikon's lineup (~US$1000), whereas management really wants progress on the upper end, where they see the margins and returns being higher. Whereas that higher end is mostly understandable and rationalized (Z6III, Z8, and Z9, with a wait on what a Z7III means), the lower end is a bit of a mess (Z30, Z50II, Z5, Zfc, Zf) because it's two different generations with two different styles. Adding a Z1 would contribute to the mess, not solve it.
