The PC market isn't dead, but then again, the Mainframe market isn't dead either. The Post-PC devices[1] (tablets / smartphones) are it for the majority of folks from here on out. They are easier to own since the upgrade path is heading to buy new device and type in my password to have all my stuff load on it. If I want to watch something on the big screen, I just put a device on my TV. Need to type, add a keyboard.…
I really don't understand your concern.
Hobbists have a wider selection of computing tools than ever before (altough, that statement was true at any time since the 50's). We have the entire arduino ecosystem for hardware hobbists, throwaway PCs like the Raspberry Pi for embebbing real computers everywhere, several different standards of desktop-capable parts for more powerfull systems, and the server ecosystem for the real beefy ones.
Most of those computer types aren't even able to run Windows or OSX. iCloud and Secureboot won't make them go away.