Backups and merging backups

I had an iPhone 3G (which after a bad drop had the home button messed up) and then I purchased the iPhone 4 months ago. Now, call it my pc sucks, hectic life, laziness, etc, but I never backed up my 3G to immediately restore to the iPhone 4. Now I'm getting the 4s and since I'm giving my iPhone 4 to a relative and need to upgrade to ios5 I'm wondering if there's a way to back up the 3G, backup the 4, merge them and then install it in the 4s.

I know I complicated myself unnecessarily, but is there any hope?