If you bought a new PC 6 years ago it probably has a dual core CPU , 2GB+ of memory , a 100GB+ HDD and some hardware accelerated graphics.
In other words enough to comfortably run Windows 7, Office, Chrome and even Photoshop.
There are still plenty of workplaces around where computers are still predominately Pentium 4s.
At work, for that entire 8 year stretch, I've done 100% of my network diagrams/power points/Boring-office-stuff on a Dell Precision 650 with a grand total of 4 GBytes of ram (That was a lot back in 2013) running (and still running) windows XP.
I think _that_ has a lot do with why AAPL is now roughly double MSFT.
Linux has traditionally maintained support for older hardware - through driver support, forums to answer questions, and Linux installations that are snappy even on old hardware.
Actually, I see desktop computing (including laptops) hitting a plateau already just from being good enough (factor in Windows XP's decades-long lifetime).
Arguably if desktops are plateauing, embedded devices will follow a similar trajectory on a shorter time scale - all the hard-knock lessons are already known.
Ultimately the year of the Linux desktop won't happen - but businesses will face fast-shrinking margins for desktops, laptops, and per-seat software licenses.
The iPad is an order of magnitude more simple than OS X or Windows, which are themselves quite a bit more user friendly than Linux.
I think something like Chrome OS is a more likely business target than Linux (thin client-ish and mostly web/cloud based).
The iPad is sort of like buying a scooter when you live in an urban area. If you already have a car you might not get rid of it, but you drive it a lot less and when it comes time to be replaced, its worth is now a conversation instead of a sure thing.