And in 2015 we will start replacing our desktops with convertible mobile devices. Slide your tablet or phone next to a keyboard, mouse, and monitor and voilà, you've got a desktop. I'm really hoping we're completely wireless on the monitor too.
Eventually low-power portable-class computing hardware will be as powerful as typical desktop systems today. Though there will likely always be a niche for even higher performance machines.
Price will come down with volume and greater competition as the market matures, as it always does.
And the OSes will get better as people spend more time on these devices and developers spend more time targetting them and working out the appropriate UI optimizations for mobile vs. desktop modes.
Already we have tablets running x86 with good enough battery life, better power than the ARM counterparts, and a full OS, with external hardware support.
Sure, it's not completely there yet, but considering it's $399 today for something that is pretty damned close (and close enough that my girlfriend just ordered one, to use for most of her primary computing, but coupled with the active digitizer for sketching; basically, a netbook), it's only a matter of time before this is completely doable!
But that gap is rapidly diminishing - the phones are catching up.
And as for user experience, you need to be able to get a "proper" desktop OS, and you need to not have to plug in lots of cables. And it needs to be able to drive a sufficiently high resolution display at good speed. It's slowly getting there, but it's got a bit to go still (but consider that today, mid-range Chinese unknown brands churn out quad core Android tablets with 2560x1600, and even low end phones come with 1920x1080 screens; and many of these devices can handle 3840x2160 output to external screens...)