I know Ubuntu 13.04 includes linux kernel 3.8. Will Ubuntu 12.10 ever update to 3.8?
Very probably: No.
Only very few packages are updated to newer versions within one release of Ubuntu (for instance Firefox). For all other packages patches for the same version are supplied to fix security issues or bugs while sticking to the version to avoid compatibility issues with other packages. Currently the developers are planning to supply an additional repository for LTS-versions of Ubuntu that includes further updates, including kernel versions, yet this is not available yet and since 12.10 is not an LTS version it will never be for that one.