The Wikipedia article says the operational altitude of the P-8 is too high for MAD. Even though the P-8 is Navy, I should think the CVNs should have some ASW aircraft of their own.
Yes , we'll never need MAD again. Just like in the 1960's it was decided that we'll never need to dogfight again. Yes, after ww1 we'll never need the bayonet again. Cruisers don't need torpedoes , we'll only fight long range daylight gun battles in the future. Escort fighters? What for? You know the bomber will always get through! Funny how those who say "the military doesn't need" are never the same people who have to go out and fight wars!. Yes I've prosecuted submarines from 20k feet. And if you are going against nuclear submarines in blue waters sometimes it even works. But did anyone notice that the majority of submarines in the world today are not big , fat nuclear steam kettels? But quite , small , diesel or AIP submarines? That's the problem with saying , "we'll never need"...the opposition looks at your strategy and says "HEY!" , "guess how you beat them? Do what they say they'll never need".
I'm not saying that MAD is absolutely "mission essential" , but I am saying is the more tools you steal from the carpenter's tool box, the lousier job the carpenter can do , as he can't do various jobs or deal with diverse problem. Soon all the carpenter's box will have in it is a hammer, and he'd damned well better pray that every adversary is a nail.
They are supposedly developing MAD-equipped UAV to work with P-8 to address the lack of MAD.
"To meaningless French Idealism, Liberty, Fraternity and Equality...we answer with German Realism, Infantry, Cavalry and Artillery" -Prince von Bülov, 1870-