As soon as everyone stops using cell phones camera sales will pick up.
and when will that be? those are always improving, take better pictures than ever, are incredibly simple to use, get firmware updates regularly, and make sharing, editing, and storing easy.
It's been my experience that the cameras in cell phones work fine when the phone is brand new, but the quality of the results degrades over time. I assume that vibration, dirt, moisture, and smudging all take their toll on the phone internal cameras.
For awhile there it seemed like the phone manufacturers and carriers had convinced the customers to buy new phones every couple of years. That was when phones cost $250-$400. Phones may now cost considerably more than that though, and customers might have grown weary of buying new phones and having to migrate everything from the old one to the new one, especially when the software on the phones has matured to the point where new features are only evolutionary, not revolutionary.
If phone shooters find a lack of reason to upgrade but also begin to feel that the camera built-in is inadequate, then that could help shift some users to separate cameras again. It won't be massively widespread, but I could see someone wanting good pictures of their family, or pictures from concerts, or pictures from events looking towards a better camera.
Now all that said, the camera manufacturers need to up their game for interoperability. I'm not a huge fan of Tony and Chelsea Northrup, but I agree with a recent video where he cites a Samsung NX mirrorless interchangable lens camera as being one of the most important cameras of the last decade, in that by being an Android-based device it had a whole slew of capabilities for interoperability and Internet storage and connectivity that was not implemented widely by other manufacturers. These features allowed users of the system to truly automatically save their contents to Internet servers, to easily livestream, to and to use various third-party services that had Android applications, on a device with a cellular data plan. The camera did for cameras what the Android Phone did for personal digital assistants, in taking what devices like the Palm Pilot did and seamlessly interconnecting to the Internet for much greater capability.
For whatever reason Samsung stopped this product line. Perhaps they introduced it too soon, before the buying public was ready. Perhaps their interchangable lens system simply was too limited at the time of release and they couldn't attract enough attention from prosumer or professional users. Regardless though, I suspect that if Canon, or Nikon, or Sony, or any other manufacturer with a large, high quality lens catalog followed this path, they'd revolutionize the market, offering both casual users and professionals alike connected features that would make the acts of saving, archiving, and sharing vastly easier than they currently are.