The "All-in-One" titles take a much broader and deeper dive in their subjects, Excel in this case. It is basically those 8 books in one, where as the Excel 2016 for Dummies title is 2-3 times shorter in length and provides a more succinct version of exactly what you need to know to operate the program successfully. However, it is also important to note that these books don't have the same content in them, yes the all-in-one will encompass Excel 2016 , but the content is different, and both books could easily be added to the same reference library.
As far as any an Access 2016 All-in-One for Dummies goes, I do not see anything in the system regarding this. But that doesn't mean it won't happen, just that there aren't any plans that Technical Support has been made aware of as of yet.
Thanks for reaching out!
Tom with Wiley