Linux is important on dekstops to thrive. I've successfully transitioned my parents to Linux. What I got? Deser maintainance, more reliability, everything just works for them.
And of course, sticking to proprietary solutions in a long run would be rather a sick idea.
That's what distros are for. The "Linux" family of operating systems are used for a very wide variety of uses, some of which are orthogonal (and sometimes incompatible) with "desktop" features.
Something like "Year of the KDE desktop" or "Year of the Linux Mint desktop" would make much more sense than trying to shove all of Linux into one pigeon hole. In fact, even within "desktop" there is variation. While an easy to use, mostly automagic desktop is a good idea, that's not the only definition of "desktop".
Ultimately, this is the the biggest problem with the idea of "THE Linux desktop"[1]: one size never fits all. Fortunately, Linux distributions exist[2] allowing for great variety - including "everything just works" desktop distributions. Just remember that the Linux ecosystem is larger than one type of distro.
[1] and systemd, and 15+ years ago the "desktop environments" that insisted there should be only one GUI toolkit, etc
[2] This assumes distros decide to keep their own identity instead of continuing on the homogeneity bandwagon that many joined when they converted to systemd. Turning into a clone of Red Hat is the path to obsolescence.
I think that pretty soon features backed by machine learning and mass data collection, features like intention comprehension and prediction or voice command/search, will be commonplace and hotly desired by users.
When that happens, I don't think the Canonical or Redhat will be able to compete, and only Google will be able to create an OS on top of Linux, and open-sourcing won't do any good because the most important services will be behind Google servers.
Linux derivatives rule the mobile space spo in essence it won really big. The desktop is not that impoortant. And so many of its paradigms are quite dated compared to the mobile experience.
Android/Linux could become tomorrow Android/BSD or Android/QNX, Android/Almost POSIX Kernel and only OEMs and people using undocumented APIs would notice.
And of course, sticking to proprietary solutions in a long run would be rather a sick idea.