Nowadays, I think 1080p screens are starting to creep into even smaller 10"-11" devices. And with the light Apple is shining on high resolution screens now, I expect this will accelerate, and we'll see more high resolution screens on laptops filtering down from specialty PC laptops to midrange ones, and extreme high resolution screens start to show up on the specialty ones.
This is a lot like how it worked in the iPhone vs. Android world of phone resolution. Android phones jumped up to 800x480, then the iPhone jumped all the way to 960x640. Android stayed at 800x480 at first, then 960x540 (qHD) screens became more common, and now a device doesn't count as a high end Android phone unless it has a 720p screen, a higher resolution than the iPhone (though usually at slightly fewer PPI because of the different screen size).
http://blogs.msdn.com/b/b8/archive/2012/03/21/scaling-to-dif...
Surface and Surface Pro will presumably have 1366x768 and 1920x1080 screens respectively (no insider knowledge here; just makes sense given the marketing materials released). This will correspond with 100% and 140% scaling.
I suspect that many if not most apps will ship at least 140% resources just to satisfy displays such as the Surface Pro will have. And realistically, most apps will probably go ahead and ship 180% if they're shipping 140%, which is sufficient to support pixel densities (slightly) higher than iPad 3.
Disclosure: I work a Microsoft; I don't speak for Microsoft; etc.
Disclaimer: also work for Microsoft, but all my info about product plans comes from devouring public information.
I'm not sure what the plan is for desktop apps on high-res devices. Hopefully the plan isn't "we'll live with tiny text" or "we'll live with fuzzy graphics", but it could be one of the two.
It is nice that this is fixed in WinRT, but we can't do the high-end productivity apps in WinRT (e.g., Visual Studio or Photoshop with plugins). I actually wouldn't mind using high-end productivity apps in WinRT (I maximize most of my apps already in desktop), and I hope in the future that will happen.
(1) Apple has made lots of forward looking investments to get long-term lock ups on supplies even if the manufacturer is Samsung. So perhaps they've already bought the next 1 or 2 years of these displays that Samsung can produce. Samsung would then have to build more factories to supply the needs of other OEMs, where the OEMs did not help invest ahead of time to help build this capacity themselves.
(2) More significantly: the operating system and its software eco-system must actively support high-resolution displays. Since Windows 8 is more popular on the low end, there might not be much incentive for Microsoft or their software partners to actively change their software to support what would initially probably be a very niche market for them. Without the software, there isn't much motivation to produce the hardware. Apple doesn't really have this problem: they've sort of forced the issue by releasing the hardware first, they've upgraded their OS to deal, they've primed the market with a few enabled apps, and their users are fairly high end, will demand more apps, where the app developers will quickly oblige (Adobe came out with a HiDPI version of the Creative Studio tools recently).
Eventually we will all get high resolution displays, but it will probably take much longer for the PC ecosystem than the Mac ecosystem. If its successful enough on Mac, however, I would expect the process to speed up on PCs so they remain competitive.