While I think Windows 8 will make up a majority of the tablet space in a few years, I don't think it will a competitor to iPad and Android.
My guess is that Windows 8 tablet will replace laptop not other tablets. Just like notebook today, the only ones that will be worth getting will be priced higher than the iPad and Android tablets. I can't imagine a netbook spec tablet being able to actually take advantage of the features that makes Windows 8 so enticing.
Yeah, the iPad is proof that people don't want tablets to be laptops without keyboards. Because laptops with keyboards are supercheap and they are available now for less than an iPad and they already run Windows. Where's the market for a laptop without a keyboard? All Windows tablets have never sold well, meanwhile the iPad shows up and sells 50 million units from launch to today.
MS is barking up the wrong tree (as usual) if they think Win8 for ARM will magically drive sales of tablets running Windows, especially since Win8 for ARM doesn't actually run any x86-native apps. Your dreams of running Photoshop on your Touchpad will remain sadly unrealized.
What really pisses me off is the drive to push Metro onto everything MS sells, I don't want fucking Metro on my Xbox 360's Dashboard, that's fucking retarded. I don't want fucking Metro on Win8 for my desktop PCs, that's fucking retarded. MS's solution to WP7 circling the drain a year after launch is to slap Metro on everything. Fuck that, and fuck YOU Ballmer.