Anyway, Linux has always been the under-dog. It was "statistically" much less likely to survive in the late-90s and early-00s.
In my personal opinion, Linux offers me the best desktop experience today.
I think I'm not in a bubble, I dabble with MacOS and Windows often. Linux feels liberating. It takes time to customize to one's preferences, but after that, it is smooth AF.
I don't even do that. I find the {mint, PopOS} defaults to be incredibly sane. I think I changed the background of mint. I'm always SO very confused when I need to use a MacOS or Windows machine.
That said, you can get the feeling out of the corner of your usage that something's gonna give. There has been painful transitionary stuff going on (remember X vs wayland? ifupdown vs networkmanager vs netplan? systemd? musl vs glibc?) that somehow the community papered over in a sane fashion for GP use, but when I was "sysadminnnig" stuff as an accessory to the stuff I was coding, it was loads of pain normalizing between different machines and moving from distro to distro. This could get even worse as stuff moves to containerized work, so the people most likely to complain due to bearing the most pain just stop caring.
It's currently dominant on phones and servers. Google can snap its fingers and set one of those on a course to drop toward zero over a few years, and is well-positioned to push Fuchsia for cloud-related server purposes if it so chooses, so that'll likely go too, if they decide to do that. AFAIK most Linux desktops are ChromeOS devices, and that's Google again.
That leaves traditional Linux desktop users, but if Fuchsia's GUI is any good and is well-integrated, and driver support is OK, those'll bleed to Fuchsia faster than they're replaced, too.
I can definitely see Google wanting to consolidate their codebase and switching all the consumer devices they maintain to Fuchsia sooner or later.
As a part time Linux desktop user since ~2002, I don't think other traditional linux desktop users would bleed to Fuchsia. I could see some people switching from macOS to Fuchsia though.
But I actually don't think this will happen with Fuchsia and I expect to just deal with the problems of Linux for another 20 years. Oh well.
In any case, given Google's lack of attention span, I suspect Linux will still be going strong another 4-5 new OS's from Google down the road.