I think we should keep unapproved separate from deleted, not only for semantic reasons, but also because access to recycling is a different permission to access to (own/any) moderated posts.
Not only would you filter them differently, you'd probably have different UI for the different types of posts; if you delete something, you're indicating that you want it out of the way, as opposed to something not yet made live.
I'd also note that I don't particularly like the idea of unapproved posts/topics being used for future-dated/blog type posts, I'd rather keep them out of the loop (keeps the main table leaner which always helps in performance terms)