I hope v2 plugins will be usable out of the box in v3 too (using the latest v3 dev build atm)
Do you have something planned for removed API?
A highlight you can add removed functions to would be helpful for those post-patch fixes.
You'll have some API maintenance work ahead anyway might as well make it useful
Example:
http://www.wowpedia.org/Patch_5.2.0/API_changes (scroll down to API tables and expand removed column)