It’s still early in the Z System’s history as I write this (four years), so probably early to give advice, but here are a few thoughts on the cameras that have had some sort of update so far:
- Z50 — The Zfc is really the Z50 II. The primary things that got added in the Zfc are USB Power Delivery, as well as some additions and performance tuning of the autofocus system. The Rear LCD goes fully swivel instead of simply tilting. The problem is that you also get a complete UI change from modern Nikon to legacy Nikon. Coupled with the mild nature of the upgrades, I generally don’t recommend that you trade your Z50 in for a Zfc. If you never use the viewfinder, the Z30 is also a Z50 II, but without the viewfinder or flash. Unfortunately, that, too, is a fool’s upgrade proposition: you’ll miss the EVF or the flash at some point in the future.
- Z6 — The Z6 II is the one camera that people might consider updating to, but it’s mostly because of how the Z6 camera is being used couples up with what was changed. The Z6 model is popular with event/people photographers. The dual card slots, availability of the MB-N11 vertical grip, and the new AF-area modes as well as improved focus performance, particularly in low light, are all welcome changes for this group of users. If you’re a video user, the added 4K 50/60P might appeal, too. Other small things may attract the Z6 user to the Z6 II, as well. Still, unless a number of those things are ones that would make your work more pleasurable, I wouldn’t recommend an upgrade.
- Z7 — Good news for you Z7 users: it’s unlikely that you need the things that changed in the Z7 II. (Many of the changes are the same as with the Z6 II.) Most people opting for the 45mp version of the camera are doing landscape, travel, and general photography. The 900 second shutter speed might be useful, as well as un-cluttering the display are probably the most interesting changes to the Z7-type user. If that’s the case, the II advances probably don’t provide you much bang for the buck. Stick with your Z7 and wait until you see what the Z7 III brings. That’s generally been my advice, anyway: skip a generation of camera before upgrading.
Should you just upgrade to a Z9? A lot of folk already have. But you’re talking about a much more expensive mirrorless camera than you had, and it’s bigger and heavier. Sure, the feature and performance list of a Z9 is extensive and state-of-the-art. However, I’m confident that Nikon will put out lower-priced models that begin picking up many of those features and performance enhancements. My advice to most is to just be patient.