If the world changes and submarines become a big issue again for some reason, we can easily buy some better, cheaper P-8s in years to come – the production line for those will be running for a good long time and prices will only fall.
I wonder if the same airframe sales room will have off-the-shelf AEOps for sale. There is no doubting that alternative and probably better airframes exist, and it appears that the UK industries are no longer 'world beating' at providing the mission kit, but once experience amongst the human part of this scenario is lost, it will be difficult to replace.
Of course there may have been an improvement in fixed underwater detection assets that mere mortals are blissfully unaware of that make this entire thread dead in the water (pardon the pun:-accidental ones are usually the best) or indeed redundant (I'm on a role now!). Of course detection is one thing; delivering depth charges and torpedoes is a differant story.
Boeing P-8. If I was an ASW crewmember (and I am not nor ever will be) then I feel four engines would be nice when operating mid Atlantic. I know Nimrod often closed down two, but at least they were there if needed. Or is salt ingestion not a factor on bypass turbofans?