Need to upgrade iPhone 6 to iOS 10 before getting iP7?

I have an iPhone 6S+ running iOS 9 and I'm getitng a new iPhone 7 this Friday. Everything is backed up daily to iCloud.

Do I need to upgrade my 6S+ to iOS 10 and do an iCloud backup to restore that backup to the iPhone 7 -- or can I use my iOS 9 iCloud backup and restore to the iPhone 7 running iOS 10?