Multiarch came a long way in 12.04. However, the 32-bit release is still recommended for download and some 32-bit debs (Google Chrome for example) still lack dependencies. I have not been able to find any blueprints dealing with multiarch for 12.10. Are there plans for improving this feature in the works or is it considered effectively complete since ia32-libs is replaced?
You can keep yourself updated through
There's another good answer covering blueprints.
As to the gist of the question: It isn't complete. It'll quite possibly never be complete. Most libraries don't need to be multi-arch co-installable, so it isn't really worth spending time on them.
Packages outside the archive (like Google Chrome) aren't likely to see much attention from Debian & Ubuntu Developers. Please check the state in the development release, and file bugs for any libraries you need, that haven't been multi-arched.