will unity become a windows 8 metro app? and will it be for arm based windows 8 stuff?
pretty granted no on the first at least.
Metro is not exactly suited for this kind of stuff, its for productivity apps for normal users or even casual mobile users.
If you talk about the built players if they go there then who knows, guess we will see as it becomes of importance. Win8 is still 9-12 months away from market.
Unsure what it will take for apps to work on Win8 in general, its the first time for Windows going there, breaking from X86 compatible exclusive in over a decade
i will love the day when i can smash my x86 computer and use a quad core tablet with a dock for keyboard. by smash my computer of course i mean put it in the top of my closet 
im just waiting for unity and a 3d modeling program for android, ios, or windows 8 arm and im gone
that day is not gonna come before 2014 or 2015 when the ARMs get fast enough. for base level usage they will become fast enough next year or the year after but for usage of heavy stuff like Unity they need to step up quite a bit further or you wait after every single click. also 8GB RAM tablets aren’t to be expected for the next 2 years I guess
wont Kal-El be fast enuf? i run a 2.4 ghz core 2 duo with 4gb of ram and it runs unity fine. and Kal-El is 1.5ghz quad core