I believe at this point we'll just go the CAPTCHA route where those that want it can enable it. This will be part of 7.1. For starters I'm not sure if we'll get an audio option in or not. Eventually we can possibly add the question/answer option as well, so admins can enable either or both if they want to wink

Anyways, that's the current major project. Definitely will support GD, possibly Imagemagick as well.