Desktops are taking a hit from iPad sales? Hmm.. have a link to back this up? Not doubting you - I'm genuinely curious.
By the way - even if iPad sales are higher than (Apple) desktop sales, and if iPad sales are on the rise and desktop sales on in decline, please do not assume that desktop sales are taking a hit because of iPads.
I call bullshit. Desktops taking a hit from tablets - are you crazy?
Desktops are taking a hit from desktops!
There are still acres of desktop real estate which is going to be replaced with more desktops.
Looking at this at a high level, there is actually pretty much sod all difference for the average user in the last 5-6 years technology-wise on a "desktop PC". They are just not buying them because nothing is compelling them to upgrade as they are fine as they are.
If there was a technological leap then we might see something but for most users, a 5-6 year old desktop would run the latest and greatest version of Windows fine.
Tablets are going to be a short lived "experiment" which will dry up in time, much as they always have been (Apple are far from being the first tablet vendor). Microsoft may have the answer to that in a hybrid device but we'll see.
I counter-call bullshit on your last part. Every time I get on a flight these days half the plan sports an iPad. On the tube, iPads and Kindles are abound. Sales trajectories aren't pointing anywhere but up. I think they left the realm of "short lived 'experiment'" quite a while ago.
Desktops aren't 'taking a hit from tablets', they're 'taking a hit from mobile platforms'. Phones, laptops, and tablets have all increased. Desktops have decreased. Tablets are chewing out part of the laptop market, but laptops in turn are chewing out part of the desktop market. Consider the desktop to laptop ratio you saw in offices 5 years ago compared to now.
I'm not saying desktops are dying, just that they're no longer 'the default' they once were.