The camera manufacturers appear to have a different view as to the purpose of Lens Road Maps than do customers.
Virtually every Japanese company provided some form of Lens Road Map when they moved from DSLR to mirrorless. The exception to that was Canon, though they apparently leaked several lenses to some customers early.
Rumor sites, meanwhile, tend to look closely at patents to try to help them predict upcoming lenses (see this site's new article about Z-mount patents). The camera companies know that their patents are being written about and providing some form of Road Map, and that's often enough for them. Moreover, the patents that don't become actual lenses are great for keeping their competitors guessing.
Over time, most camera companies have moved from having formal road maps to sometimes just providing some early information about a lens (or lenses) they're about to announce. The official Road Maps tend to go away after time, while the ones that remain get updated less frequently. For instance, OMDS, Panasonic (m4/3), and Sony no longer have an official Lens Road Map. Canon never had one.
Why is that?
Here's my take: the camera makers see Road Maps solely as statements that say "see, we're serious that we're going to produce a bunch of lenses for this new mount." They see a Road Map only as an affirmation that they're committed. In Canon's case, they've been stalling the commitment declaration because they still are trying to sell DSLRs and clear the inventory there. By the time they do, Canon will have enough RF lenses that they almost certainly will feel that they don't need a Road Map ;~).
Customers, on the other hand, are trying to plan. We use Road Maps to assess whether or not a new mount is going to actually provide the products we want, and to budget our purchases over time. We also use them—along with available lens lists—to gauge what kind of options we would have if we were to move from our current system to a new one.
Thus, I would argue that the camera makers who wish to attract customers from another mount absolutely need a Lens Road Map, need to keep it up to date, and need it to be as inclusive as possible to future products, even ones that are two years out.
Which brings us to mount adapters. Both Canon and Nikon have relied heavily on their DSLR-to-mirrorless adapters to hold their current customers. The argument is that "see, you don't need any new lenses." Right. Somewhere within the camera company is another group that wants to sell more new lenses ;~). For instance, Nikon has a publicly stated goal of increasing their lens-to-camera sales ratio from the old 1.5-1.6x all the way up to 2x. You don't do that with mount adapters.
So let me get to the answer to the headline's question: yes, I believe Nikon will provide one more Z-mount Lens Road Map, probably coincident with the next major camera release. From there, it gets impossible to predict. By the time we get to the end of the next Lens Road Map we'll probably have 40 or so Z-mount Nikkors available, and Nikon has already publicly committed to 50 by 2025. I suspect Nikon will think that this is enough information for customers, and go back to their "surprise, this is what you get next" paternalism.
Which brings me to one of my on-going criticisms of the Japanese camera makers: they claim to be systems providers, but they constantly balk about talking much about the system (unless they've got a new component of it to introduce). There's too much "sell boxes to consumers" mentality going on, and not enough embracing the customer in the long view. Even as a professional, I can't really afford to be doing full system replacement every five years. You and I both need a better understanding of how our chosen system is going to grow over a much longer period than that. Of course if it isn't going to grow, but rather be replaced by something yet again, we wouldn't be buying it, would we?
At one time in my long tech career, I had the job title of Senior Evangelist. The role of technology evangelist is to help customers understand where things are, where they're going, and how that will be better than another choice. We really don't have such a position in the camera industry. We customers tend to get what we get when we get it, and a product goes (or doesn't go) viral for a moment as the so called media that mostly gets paid via promotion races to collect its commission for pushing it. I'd say that's doing it the hard way. But apparently the Japanese camera companies don't want to do it the easier way.
Update: Note that I don't consider an update that takes a lens from being a silhouette to a revealed lens with specifications to be an "updated Road Map." A new Road Map would be one with additional, previously unknown lenses on it.
