According to this article David Helgason says…
“Unity 4, which is currently in beta, will allow the targeting of the new platforms coming from Microsoft. The v4 beta is available today, if you pre-order v4. That said the Windows 8, Windows Phone 8 parts of v4 are not yet available (but coming soon).”
Is there any ETA for the Windows Store deployment yet?
And will Windows Store deployment be possible with an update to Unity 3.x as well?
Thanks