For me shipborne UAVs of different ranges will be the most likely option to succeed for the role of maritime patrol. As commented before, long range shipborne UAVs plus some fast strategic bombers with anti-submarine capabilities are a right combination to replace the current fleet of maritime patrol aircrafts (Be-12, Il-38 and Tu-95/142). Note that the last is a strategic bomber adapted.
I appreciate what you are suggesting, and to a degree I agree... unmanned platforms have a significant future in terms of long range patrol and surveillance.
The issue I have is a ship based system will need to be rather small and short ranged even though it can move with the ship it is based upon.
To replace an MPA you will need a rather larger aircraft with bigger sensors and heavy equipment... something you wont get in a ship based system.
Of course that does not mean it can't be done... some large land based patrol aircraft of modular design that can perform each of the roles of manned MPAs would allow a reduction in size by not making them capable of doing everything.
Land basing means larger platforms with bigger sensors and the option for rearming or loading mission specific weapons fairly readily.
The ship based UAVs could link up with the long range UAVs and share data and cooperate in various situations... in fact... imagine a situation where sensor data is not good enough... you would not risk a manned MPA as they are too expensive and risk capture of crew, and a large land based UAV would compromise technology and also not be cheap but having a small ship near the contested waters that launches a smaller more disposable UAV with sensors and weapons that could innocently get lost and stray into the wrong area to either collect data or be shot down... if you know what I mean... sharing data right up the destruction with any long range UAVs in international air space nearby.... sort of like the way the US military used its recon aircraft built from modified bombers to test and probe Soviet defences... record procedures and frequencies and to look for force levels etc.
Also to see the Ka-50/52 entering in naval roles is positive. I tend to think that this helicopter will also be selected for anti-submarine role, increasing the standardization of the fleet. The Ka-29 and the Ka-52K may not be exactly of the same role, but it is possible to do a replacement adapting also the roles better to the real needs.
The different roles require very specific and very different equipment, sensors and weapons. For the Ka-52 to be used as an anti submarine helo it would need a lot of extra equipment like a dipping sonar. Its radar would be excellent for detecting things like snorkels and periscopes already, and it would already be able to carry anti sub torpedoes and depth charges including guided ones.
Personally I think a better solution would be a modular helo like a scaled up Ka-226T where the engines and rotors and front cabin are standard but a range of rear pods could be attached or adapted depending upon the role.
That way you could have a transport module for a boarding team to be carried or an anti sub module with dipping sonar and sonabouys and even a MAD detector.
For rescue you can have onboard medical equipment and a hoist.
For attack you can have something that looks like the Ka-52.
You could even use the base model as a flying crane that could fly out and lock on to surfaces mini subs to fly them back to the mother ship or to recover used sonobouys or divers...