Ask Microsoft how well the Win 8 tablets are selling.
I don't think a strong consumer demand exists for a desktop class OS on a tablet.
I don't expect to see Apple pioneer this type of development.
Microsoft is going to have to really up their game and deliver a holistic product (hardware + OS + ecosystem with relevant software) that provides a good user experience.
Unfortunately, I expect Microsoft is going to continue to muddle around, like they did with the original WinXP tablets, and with UMPC, and now with Win 8 tablets. Great hardware, OS that is half-baked, and a complete lack of applications that are written for use on a tablet. I had a Everun UMPC in 2008-2009, a great portable tablet with no useable applications.
And as long as microsoft continues screwing the pooch, Apple will continue producing iOS devices and laughing their way to the bank.
Would I buy one? If Apple produced one, yes. Not because I love OSX (which I don't, depute using a MBA to type this). I would buy it for the utility, and also because Apple actually gets that the user environment is more important then the technology.
Microsoft stops with the technology, and expects some third party will step in to develop useful applications. Which has never happened.