If they keep making a few Enterprise phones
Running WP10, but maintaining a superb camera, then it is still a very nice system.
The 950 available now (£300, damn cheap, with a Continuum adaptor) will keep the diehards like me, who don't need an app for everything, happy.
Web pages often do the job, Amazon are dropping their WP app for instance.
UWP would allow them to wrap their web pages in an app, along with automatic login etc. so that it presents more like a full app.
The cons: The TripAdvisor WP8.1 app is beautifully presented, the web wrapper, not so much.
The pros: The web wrapper app has all the web page functionality and matches the web page operation, for easier use.
It will be interesting to see if many more UWP apps appear and thus more for the phone and perhaps some OEMs start making phones again.
As for a burning platform, also not so much. WP10 gets updates along with Win10 and the anniversary edition will come to the phone at roughly the same time.
There is a lot of benefit to having the same codebase, despite some obvious UI issues. Since the phone-only platform, updated through MNOs etc., was less than successful, it is a moot point as to whether one prefers WP10 or not.
The UWP Maps app is a perfect case in point, it now allows multiple, simultaneous search tabs on a map, even on the mobile version, incredibly useful and only present because the App written for the PC added the feature. As of now, using HERE map data, the WP10 Maps is superior to the preceding HERE maps/navigation system, Cortana integration, search tabs, live Traffic Camera snapshots, multiple routes, auto-rerouting, manual rerouting, still has 3D buildings, rotation, angle, Cityscape, auto-zoom, all with offline maps stored on the SD card, brilliant and indispensable, especially when abroad.
And the Office apps have hugely more capability now because they are UWP.
I do hope a ton of companies do UWP apps, Banking for instance would be a good target, allowing the banks to use the higher security available with UWP to increase safety and being able to have a mobile version with little or no extra development.