The UK MR force operated without AAR for most of its life, and Nimrod MR only acquired AAR capability because of the Falklands. Why is it a must have now?
Why don't you write and ask the USN and Boeing instead of asking such daft questions on here. All the P8s ordered so far come with an AAR capability, can't really see ours being any different can you? But then you probably already knew that!
S-D