Or is it? Whether or not we have come close to TYOLOTD depends on how you define "The Desktop". If "The Desktop" is a metaphor for "the hands of the non-specialist user who doesn't even call their device 'a computer" then yeah, it's doing great. The Deck is a major step forwards in that, it wraps up Steam's entire catalog of Windows games into a nice little bubble of virtualization that varies in seamlessness depending on how new the game is.
If you define it as a desktop computer, it's nowhere near that. Most people who sit down at a a desk with a large screen to do work that involves multiple windows and a mouse pointer are still sitting in front of a box that's running Windows or MacOS. Those two operating systems still dominate that domain, as well as the world of people popping open a laptop to do windows-and-pointer work away from their office.
Linux keeps nibbling at that domain, and the work Valve did on their fork of WINE to get fifty bazillion Windows games running on this handheld Linux device is probably going to help take some bigger bites. But what do people go buy when they want A Computer? When you answer that with "Linux", that's The Year Of Linux On The Desktop.