Has Apple made any announcements that they will patch Krack on iOS 10-only devices?
The answer to both questions is... probably. :/

There seems to be some speculation as to whether it has or hasn't but there's a very detailed post on Stack Exchange's security site: https://security.stackexchange.com/questions/172721/did-ios-11-1-fix-krack-for-only-iphone-7-and-newer