Windows 10 MAY not formally support certain versions of Word, Excel etc.
While I am sure Microsoft will test them I think there are some versions of Word and Excel which are not officially supported under Windows 8 even.
If you are happy with Windows 7 don't go to Windows 10, certainly not at first.
Also note if you do go to Windows 10 and don't like it you probably wont be able to go back to Windows 7.