Since .NET isn't dead in Windows 8 after all, I decided to start making a managed wrapper for DirectX. Keep in mind textures don't work yet, and it is still a work in progress, but here's the most recent build on GitHub (even got it to pass certification now in Release build).
NOTICE: I'm calling this a draft, not even an alpha version at this stage. The sample app at the moment draws a triangle, but it's mostly a proof-of-concept app at this point. This work will later be incorporated into 3DAPI (also on GitHib) for true cross-platform 3D apps between Windows, Linux, Windows Phone, and Windows 8
As usual; contributors are welcome using the standard methods on GitHub, such as creating a branch and requesting a merge. If you want to be part of a big open-source project, feel free to contribute. This is currently the best alternative to XNA/SlimDX at the moment (both XNA and SlimDX have no metro support that I'm aware of, and XNA has always supported only 32-bit builds, so this seems to be a possible alternative at the moment)