No, there is no preview for updates, but you already knew that. We have preview when editors make updates, so such a feature is feasible. I don't expect schedules from volunteers so I won't say anything more about when such might become available. Certainly don't hold your breathe. (:

I think a scheme that might scale better would be to post an improved answer and let Q+A Editors remove duplicates (and do other clean-up if needed).

1. This allows all to notice the improved answer immediately (even if it takes 2 weeks for a Q+A Editor to do something about it)
2. This means all can help with improving the content instead of forcing only Q+A Editors to write improved "copy"
3. This likely reduces the amount of admin work required by editors (Q+A Editors can't delete replies to answers so they'd have to get 3 editors to help them, while they can, acting alone, delete a duplicate answer)

For trivial updates, a /msg to Q+A Editors is probably preferred.