The background When Nikon introduced the Z System, they also introduced an FTZ adapter so that DSLR users could use their existing lenses with the new mirrorless system. The problem with the FTZ adapter was simple: it didn't autofocus with all DSLR autofocus lenses; you could mount a screw-drive lens, but it wouldn't autofocus on a Z System camera.
Screw-drive lenses are ones which don't have a motor built into the lens (AF-I, AF-S, and AF-P lenses do have such a motor). Instead, they require the camera to have a lens focus motor, and it is engaged via a shaft that extends through the camera's lens mount into the lens (the screw-drive).
A number of significant lenses were left in the cold by the lack of screw-drive support: 17-35mm f/2.8, 20mm f/2.8, 24mm f/2.8, 28-70mm f/2.8, 35-70mm f/2.8, 80-200mm f/2.8, 105mm f/2 DC, 135mm f/2 DC, 180mm f/2.8, and the 200mm f/4 Micro-Nikkor. One DX lens also needs to be added to that "significant" list: the 10.5mm f/2.8. I use "significant" to describe these lenses as they don't exist in AF-S (F-mount) or Z-mount form, and were in use by a large number of DSLR owners.
Complaints about no screw-drive support were instantaneous, and not really addressed by Nikon subsidiaries or executives, despite being asked repeatedly about whether such support would ever appear.
This wasn't the first time this lack of support has happened. Back when the D40 was introduced in 2006, Nikon took out the screw-drive mechanism, and that was true for pretty much all subsequent truly consumer DSLRs made afterwards; only the prosumer and pro DSLRs had in-camera focus motors and the necessary screw-drive mechanism. The complaints about the FTZ were basically the same as they were with the D40 and subsequent consumer DSLRs, and Nikon's lack of real response to those complaints was the same, as well.
The rumor About 10 days ago, a post in China resurfaced the rumor that Nikon is preparing an FTZ adapter that supports lenses that require a camera motor, the so-called screw-drive lenses that were typical in the early D era. This was quickly followed with a more specific post that said "Nikon [will] announce a Z-mount adapter for [screw-drive] lenses next year." As usual, this was picked up first in Japan by sites such a Digicame-info, and then onto other sites such as Nikon Rumors. From there, threads on the usual fora started appearing about the rumor, often with the same participants who've been asking for such an adapter for six years.
The discussion Nikon has long been the top interchangeable lens camera brand with deep legacy support (Pentax would be the other, but didn't have the market share Nikon had in the digital age). But that legacy support has not been complete. A number of dead ends exist in Nikon's technology over their history, but I'd say that getting rid of screw-drive is probably the most important and most contentious.
People buy lenses to specific purpose. A good case in point are the two DC lenses or the 200mm f/4 Micro-Nikkor. These provide unique abilities that have not resurfaced in an AF-I, AF-S, AF-P, or Z-mount lens. Not being able to use these lenses to full potential with your latest camera is problematic, and in essence violates the whole notion of interchangeable lens mount. People want the lens look they paid for, but they also want to move with the times and get current technology cameras.
The "easy pickings" for Nikon are over at this point. In my surveys of long-time DSLR owners I find three groups: (1) convinced they'll stay DSLR and forego mirrorless; (2) want to give up DSLR but won't until the products they use are in the mirrorless world; and (3) those that have either already dipped a toe into the Z System or embraced it fully. #3 was the easy pickings. The next easiest picking is finding a new customer entirely, which Nikon's marketing isn't always up to the challenge of doing, though it's had a few modest successes at that recently.
That #2 group is hung up with something that wasn't brought over from the film/DSLR legacy. The number one and number two answers about what that is are: (a) no D7500 or D500; and (b) no screw-drive lens support. That list used to include (c) no D5/D6, (d) no D850, (e) no Df, and a few other things, but Nikon has picked most of those off and transitioned those folk to mirrorless pretty successfully. I know that Nikon does surveys similar to mine, so they must know all this (though they survey the full spectrum of customers and I mostly survey what would be called prosumer users).
So the question becomes is Nikon really going to go after (a) and (b) now? To some degree, the Z50II is poking into (a) territory (I'll have much more to say on that when my review of the camera is done). Now we once again have the resurfacing of a rumor about (b).
Here's my problem (and Nikon's): Nikon is no longer selling those screw-drive lenses. Yes, you can still get some of them new via hanging inventory, but I'm pretty sure that manufacturing is done for them. Thus, Nikon doesn't get as big a bang for their buck by producing an FTZ-screw-drive adapter today as they would have six years ago. Putting such an adapter on the market in 2025 really only lets a few folk pull a lens they already own off their shelf to use, and an even fewer number of folk would buy new Z System bodies because they could now transition properly.
Thus, there has to be a discussion of whether an FTZ-screw-drive adapter is still a "viable product." By that I mean, once you account for all R&D and move-into-production costs, do you get enough return on investment (ROI) back to justify it? If you believe you can get a higher ROI doing something else with that same money and assets, a company the size of Nikon* is should do that, instead.
True, there's the buzz-worthiness of such a product to account for (e.g. "Nikon still treats its legacy customers well."), but Nikon has turned into a company that's exceptionally efficient at generating profit on investment. The company is no longer chasing market share, bragging rights, or completeness; instead it's creating product lines everywhere that are efficient at driving financial return.
So do we believe the rumors, or not?
I believe that Nikon has had a working version of an FTZ-screw-drive adapter for some time. I once heard a credible story out of Tokyo about a photographer I won't name having tested it. It's not engineering that's keeping such an adapter off the market. It really all drives back to ROI. How many would Nikon sell, and what's the GPM? I don't know the latter number, but my surveys say that the first number isn't as high as some seem to think.
My conclusion is simple: Nikon could come out with such a product. Only the bean counters in Tokyo know whether or not they should, or not. On the impossible-to-certain continuum**, an FTZ-screw-drive adapter comes in at "possible."
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* I knew that description would get a rise out of you. For the current year Nikon Imaging is forecasting total sales of US$2b with a 15.4% profit return. A US$150 product doesn't move the bar much unless it sells in high quantity. Create too many lower cost, low volume products and you start having problems keeping that profit margin up, as you spread a lot of your existing production, inventory, sales, and marketing efforts over products that are not bringing the same level of gain.
** Impossible, improbable, possible, probable, certain.