The following article on wired is controversial, because people misread it, and perhaps the author over stated the situation.
Why Microsoft Has Made Developers Horrified About Coding for Windows 8
Go ahead and read it all, including the comments and the linked blogs. The following is my opinion:
The real problem developers and software manufacturing companies have is that existing software can become less relevant as it will be apparent it runs on abandoned technologies. Key terms sometimes used to promote own product as edgy and top of the line will lose meaning when WPF becomes a bastard child. Investment into Silverlight as a web platform by web authors will sink even faster and developers who invest their time and money into education in these technologies will also feel they were duped by Microsoft and lost the investment.
Now here’s a point I’d like to make: I doubt the non x86 tablets will run older API-s, while the desktop windows 8 will surely do. So while we can now deliver WPF based applications to Windows 7 tablets such as ViewPad, that might not be the case in the near future; Investment and time lost.
And to be clear, I don’t have any insider info regarding what Microsoft does. I just assume they won’t release an OS for tablet that takes %75 of available hard drive like it does on the ViewPad, so the only logical step is to remove the legacy bloat.