How can aircraft carriers evolve with today's technological advances ?
How will they evolve in the face of new threats such as hypersonic missiles, stealthy submarine drones... ?
They will evolve, probably to have better onboard defenses themselves. I wouldn't be surprised if the later Fords got several racks of Mk41 VLS, 16-32 cells per location and probably fore and aft, port and starboard, replacing the ESSM launchers. Just angled outboard enough to keep any boosters from landing on the deck instead of being strictly vertical. Radar capable of guiding all that as well, so full SPY6 with fixed arrays. (That applies to all ships, really. More missiles necessary for their own defense because they cannot mass together for safety in an A2AD area.)
Underwater protection is going to be an interesting discussion. The best defense against a submarine is another submarine, not a surface ship or aircraft, but a carrier can definitely add some torpedo defenses.
Will the trend be towards larger aircraft carriers or smaller ones ? Could we see "very light carriers" again ?
The bigger the carrier the better. Gives you more space for longer catapults, more arresting gear run, more space for bigger aircraft. The 6th Gen fighters are going to be huge, the range requirements demand it. I figure the USN F/A-XX is going to be on the order of 85klbs, right at the limit for the catapults and arresting gear, and bigger than a Flanker in bulk. And the USN 6gen is going to be the
smaller plane than the USAF 6gen, I'm expecting that one to be over 100klbs!
I think the 100ktons size is about the max anyone could afford to build. Something the size of a Nimitz or Ford.
The smallest carrier capable of doing anything beyond protecting itself is going to be about 45ktons. Midway sized.
We are NOT going to see 12kton CVEs show up. A convoy escort needs to be able to handle a minimum of 20 aircraft:
2-3 AEW, to keep one in the air 24/7 (5-7 if you need to use helicopters for AEW, helicopters have much less endurance)
8 fighters, to keep two in the air 24/7
4 ASW helicopters, minimum, to keep one in the air 24/7
2-3 utility helicopters as plane guard and CSAR, to keep 1 in the air 24/7
2-3 COD cargo planes
Are stealth aircraft carriers a possibility ?
Maybe? First, you'd need to do something weird for the hull shaping. Slapping an island shaped like the Zumwalt deckhouse is trivial. Then you have all the aircraft on deck in very unstealthy condition, and all the people and tugs running around, all equally non-stealthy.
Even if you could reduce the RCS of a carrier to the size of a B-2, now there's a carrier sized hole in the reflections from the water and that huge wake a quarter million horsepower makes in the water.