For the premium plugin SCEditor, I have implemented the shortcut CTRL+ENTER to submit posts. It is like on github and stackoverflow.
It kind of annoys me that this shortcut is missing here in the main q2a forum =)
If we stick to CKEditor, the shortcut can be added in the config.js with:
config.keystrokes = [
[ CKEDITOR.CTRL + 13, 'save' ],
// not tested though
PS: I have implemented this in the SCEditor plugin, see post here.