Speaking from a working photographer's perspective, who uses Nikon cameras on a daily basis:
Ditch the compact camera range - who buys them anymore if they already own a smartphone?
Ditch the KeyMission range - Nikon arrived too late in the game.
Produce a DX and FF mirrorless camera. I'm jealous when I see a wedding photographer using a Sony a7II because there is no mirror 'clunking' during the ceremony.
Produce more professional DX lenses.
Update existing, but old, lenses at a greater rate.
Consider entering the medium format market.
Read photography forums to see what users are saying about their existing equipment, and to read about what people are expecting/would like in future equipment.
Improve the DSLR video capabilities (codecs, and video focussing) so they can compete with Canon in this area.
Stop increasing prices. Nikon is facing stiff competition from Sigma and Godox for lenses and flashes respectively. These third party products are now incredibly good (and in many cases, outperforming the Nikon equivalent) and cost about half the price.
Stop crippling cameras with weird firmware/software decisions:
1. Why can't a Nikon camera with wi-fi built in transfer files to a Mac or PC. Why are the applications only available for iOS and Android? Many photographers want to send images to a laptop or desktop computer so they can view and edit the images immediately as part of their workflow (events, studio portrait and still life, for three quick examples).
2. Why can't a Nikon, when tethered, display the image that has just been captured in the camera screen? The tether cable needs to be unplugged to carry out a quick image review, which is crazy! I often have a camera tethered and the computer is a fair distance away. I need to either walk over tot he computer or unplug the tether, which is maddening! I wouldn't need to still operate with a tether if Nikon allowed me to use the camera's wifi to connect to a computer (see point 1!)
3. Unless I own the top of the range Nikon, why can't I lock the setting dials to prevent unwanted shutter speed and aperture adjustments when I am working on a job where they are fixed (eg with studio flash where the power output of the flash won't be changing for duration of the day). It is insane I need to place tape over the dials on a 2k camera to prevent them being knocked accidentally, otherwise I run the risk of taking a series of shots with the wrong exposure, and I don't notice the error because I can't review the images on the camera whilst taking them (see point 2!).
4. Allow me to change the aperture when using live view for photos or video.
5. Crosshair autofocus points in other regions of the view other than directly in the centre of the frame. Placing a few on the 1/3rds lines would be really bloody useful!
As far as I know, Canon cameras allow users to do all of points 1-4.
I use Nikon because I'm so heavily embedded into the Nikon ecosystem with their equipment or Nikon compatible 3rd party equipment (lenses, flash, wireless triggers). If it were as simple as choosing a different camera body then I'd be switching to Canon or Sony immediately...
As a new customer without any existing equipment burden, I honestly don't know why anybody would choose Nikon right now over the competition.
I love the image capture quality of the Nikon equipment I own. Weirdly, improving that is the last thing they need to do to prevent me from eventually changing brands - at vast expense
