In the translation tool, You can see auto saving process while translation. It will be very helpful if VE also can provide auto saving as draft. After drafting if someone wants to publish so it's okay. But if someone wants to do more work so it will be helpful for editor. I hope I have explained myself properly.
Topic on VisualEditor/Feedback
I'd just like to note that this should not be considered related to VE.
VE is a minor secondary editor. Almost all edits are made using the Wikitext editor. If it is decided that some sort of auto save for editing should be is added, then I naturally support adding the feature to the secondary editor as well.
I would really like to see this feature as well.